TST: DatetimeIndex and its Timestamp elements returning same .weekofyear with tz (#6538)
 - [x] closes #6538
 - [x] tests added / passed
 - [x] passes ``git diff upstream/master --name-only -- '*.py' | flake8 --diff``

I think this was closed by PR #15740.

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16181?src=pr&el=h1) Report
> Merging [#16181](https://codecov.io/gh/pandas-dev/pandas/pull/16181?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/de8734474daddf772d97c66a9ef759e23a3d362f?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/16181/graphs/tree.svg?width=650&height=150&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/16181?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #16181      +/-   ##
==========================================
- Coverage   90.88%   90.86%   -0.03%     
==========================================
  Files         162      162              
  Lines       50821    50821              
==========================================
- Hits        46189    46177      -12     
- Misses       4632     4644      +12
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.64% <ø> (-0.03%)` | :arrow_down: |
| #single | `40.33% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16181?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/16181?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `63.54% <0%> (-1.82%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16181?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/16181?src=pr&el=footer). Last update [de87344...042ad24](https://codecov.io/gh/pandas-dev/pandas/pull/16181?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/16181?src=pr&el=h1) Report
> Merging [#16181](https://codecov.io/gh/pandas-dev/pandas/pull/16181?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/de8734474daddf772d97c66a9ef759e23a3d362f?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/16181/graphs/tree.svg?height=150&src=pr&token=eZ4WkYLtcO&width=650)](https://codecov.io/gh/pandas-dev/pandas/pull/16181?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #16181      +/-   ##
==========================================
- Coverage   90.88%   90.86%   -0.03%     
==========================================
  Files         162      162              
  Lines       50821    50821              
==========================================
- Hits        46189    46177      -12     
- Misses       4632     4644      +12
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.64% <ø> (-0.03%)` | :arrow_down: |
| #single | `40.33% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16181?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/16181?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `63.54% <0%> (-1.82%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16181?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/16181?src=pr&el=footer). Last update [de87344...042ad24](https://codecov.io/gh/pandas-dev/pandas/pull/16181?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Thanks!