DOC: fix pd.to_datetime documentation (issue #14448)
Dupe of #14452
- [x] closes #14448
- [ ] tests added / passed
- [ ] passes `git diff upstream/master | flake8 --diff`
- [ ] whatsnew entry

## [Current coverage](https://codecov.io/gh/pandas-dev/pandas/pull/14456?src=pr) is 85.25% (diff: 100%)

> Merging [#14456](https://codecov.io/gh/pandas-dev/pandas/pull/14456?src=pr) into [master](https://codecov.io/gh/pandas-dev/pandas/branch/master?src=pr) will increase coverage by **<.01%**

``` diff
@@             master     #14456   diff @@
==========================================
  Files           140        140          
  Lines         50631      50631          
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
==========================================
+ Hits          43166      43167     +1   
+ Misses         7465       7464     -1   
  Partials          0          0          
```

> Powered by [Codecov](https://codecov.io?src=pr). Last update [c31ea34...5890a0d](https://codecov.io/gh/pandas-dev/pandas/compare/c31ea341747ac40d83e64d00bac179548e4b716e...5890a0db44e6b07c2033deca0d6a980f6417300f?src=pr)
 Ah, it's dupe with #14452. Appreciate your review on #14452.
