BUG: fix tz-aware datetime convert to DatetimeIndex (GH 14088)
- [x] closes #14088
- [x] tests added / passed
- [x] passes `git diff upstream/master | flake8 --diff`
- [x] whatsnew entry

## [Current coverage](https://codecov.io/gh/pydata/pandas/pull/14090?src=pr) is 85.26% (diff: 100%)

> Merging [#14090](https://codecov.io/gh/pydata/pandas/pull/14090?src=pr) into [master](https://codecov.io/gh/pydata/pandas/branch/master?src=pr) will decrease coverage by **<.01%**

``` diff
@@             master     #14090   diff @@
==========================================
  Files           139        139          
  Lines         50492      50492          
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
==========================================
- Hits          43053      43052     -1   
- Misses         7439       7440     +1   
  Partials          0          0          
```

> Powered by [Codecov](https://codecov.io?src=pr). Last update [185fcbe...c91425b](https://codecov.io/gh/pydata/pandas/compare/185fcbebd8c65706a9e3fea2d1ae28aa2d8baa93...c91425b8bd8100c588c59fe085f664a20d5844d9?src=pr)
 thanks!
