CLN/DEPR: remove setter for MultiIndex levels/labels properties
Noticed this in another PR, this doesn't seem to be listed in our deprecations master issue https://github.com/pandas-dev/pandas/issues/6581. But it is already deprecated since 0.13 (https://github.com/pandas-dev/pandas/pull/4039)
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18256?src=pr&el=h1) Report
> :exclamation: No coverage uploaded for pull request base (`master@7b5ca80`). [Click here to learn what that means](https://docs.codecov.io/docs/error-reference#section-missing-base-commit).
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/18256/graphs/tree.svg?width=650&height=150&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/18256?src=pr&el=tree)

```diff
@@            Coverage Diff            @@
##             master   #18256   +/-   ##
=========================================
  Coverage          ?   91.39%           
=========================================
  Files             ?      164           
  Lines             ?    50092           
  Branches          ?        0           
=========================================
  Hits              ?    45780           
  Misses            ?     4312           
  Partials          ?        0
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.2% <100%> (?)` | |
| #single | `40.36% <100%> (?)` | |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/18256?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/indexes/multi.py](https://codecov.io/gh/pandas-dev/pandas/pull/18256?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9tdWx0aS5weQ==) | `96.38% <100%> (ø)` | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18256?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/18256?src=pr&el=footer). Last update [7b5ca80...a393159](https://codecov.io/gh/pandas-dev/pandas/pull/18256?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/18256?src=pr&el=h1) Report
> Merging [#18256](https://codecov.io/gh/pandas-dev/pandas/pull/18256?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/7f4c960c7d0c100e5df9f0a3bc68401fc4eace4d?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/18256/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/18256?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #18256      +/-   ##
==========================================
+ Coverage   91.38%   91.38%   +<.01%     
==========================================
  Files         164      164              
  Lines       49884    49879       -5     
==========================================
- Hits        45584    45582       -2     
+ Misses       4300     4297       -3
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.19% <100%> (+0.02%)` | :arrow_up: |
| #single | `39.41% <100%> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/18256?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/indexes/multi.py](https://codecov.io/gh/pandas-dev/pandas/pull/18256?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9tdWx0aS5weQ==) | `96.38% <100%> (-0.02%)` | :arrow_down: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/18256?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/18256?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.8% <0%> (-0.1%)` | :arrow_down: |
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/18256?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `65.25% <0%> (+1.81%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18256?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/18256?src=pr&el=footer). Last update [7f4c960...9c3ad6f](https://codecov.io/gh/pandas-dev/pandas/pull/18256?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Failure only seems to be the clipboard one (which is known), and the BUILD_TEST. 
Not sure why that last one is failing already tried to restart it some times) > Failure only seems to be the clipboard one (which is known), and the BUILD_TEST.
Not sure why that last one is failing already tried to restart it some times)

assume you have rebased on master. These failures are not longer. your build looks old (e.g. not rebased) lgtm otherwise (but push again anyhow) This *was* from a clean master, at the moment the PR was opened :-) 