DOC: cleanup build warnings
## [Current coverage](https://codecov.io/gh/pydata/pandas/pull/14172?src=pr) is 85.25% (diff: 100%)

> Merging [#14172](https://codecov.io/gh/pydata/pandas/pull/14172?src=pr) into [master](https://codecov.io/gh/pydata/pandas/branch/master?src=pr) will not change coverage

``` diff
@@             master     #14172   diff @@
==========================================
  Files           139        139          
  Lines         50496      50496          
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
==========================================
  Hits          43049      43049          
  Misses         7447       7447          
  Partials          0          0          
```

> Powered by [Codecov](https://codecov.io?src=pr). Last update [8023029...9a0f983](https://codecov.io/gh/pydata/pandas/compare/80230292e19e377f5b11409e112500b6a180e18a...9a0f983beee6ba964ca32c6f537b66e93d44cbb7?src=pr)
 minor comments, lgtm.
