Issue/26506 Provides correct desciption in docstring that get_indexer methods are not yet supported
- [x] fixes docstring for #26506 until implementation is ready
- [x] 46585 tests passed - none added as documentation change only
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
```
$ git diff upstream/master -u -- "*.py" | flake8 --diff && echo yes
yes
```
- [x] whatsnew entry
Provides correct desciption in docstring that Interval.get_indexer using any method other than default are not yet supported
