Update link in the deprecation message for .ix
The anchor on the indexing.html page has changed, this updates the link in the warning message


# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=h1) Report
> Merging [#16691](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/344cec77f1904343f8d253d7cfd8d5fccddb08de?src=pr&el=desc) will **decrease** coverage by `0.02%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/16691/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #16691      +/-   ##
==========================================
- Coverage   90.95%   90.92%   -0.03%     
==========================================
  Files         161      161              
  Lines       49276    49276              
==========================================
- Hits        44817    44805      -12     
- Misses       4459     4471      +12
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.68% <ø> (-0.03%)` | :arrow_down: |
| #single | `40.18% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/indexing.py](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhpbmcucHk=) | `94.01% <ø> (ø)` | :arrow_up: |
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `63.23% <0%> (-1.82%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=footer). Last update [344cec7...1c44ba6](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=h1) Report
> Merging [#16691](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/344cec77f1904343f8d253d7cfd8d5fccddb08de?src=pr&el=desc) will **decrease** coverage by `0.02%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/16691/graphs/tree.svg?src=pr&token=eZ4WkYLtcO&width=650&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #16691      +/-   ##
==========================================
- Coverage   90.95%   90.92%   -0.03%     
==========================================
  Files         161      161              
  Lines       49276    49276              
==========================================
- Hits        44817    44805      -12     
- Misses       4459     4471      +12
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.68% <ø> (-0.03%)` | :arrow_down: |
| #single | `40.18% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/indexing.py](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhpbmcucHk=) | `94.01% <ø> (ø)` | :arrow_up: |
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `63.23% <0%> (-1.82%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=footer). Last update [344cec7...1c44ba6](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=h1) Report
> Merging [#16691](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/344cec77f1904343f8d253d7cfd8d5fccddb08de?src=pr&el=desc) will **decrease** coverage by `0.02%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/16691/graphs/tree.svg?height=150&width=650&token=eZ4WkYLtcO&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #16691      +/-   ##
==========================================
- Coverage   90.95%   90.92%   -0.03%     
==========================================
  Files         161      161              
  Lines       49276    49276              
==========================================
- Hits        44817    44805      -12     
- Misses       4459     4471      +12
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.68% <ø> (-0.03%)` | :arrow_down: |
| #single | `40.18% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/indexing.py](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhpbmcucHk=) | `94.01% <ø> (ø)` | :arrow_up: |
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `63.23% <0%> (-1.82%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=footer). Last update [344cec7...1c44ba6](https://codecov.io/gh/pandas-dev/pandas/pull/16691?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks!