Updated the return type section of to_datetime 
Updated the return type section of to_datetime to include list-like mixed timezone inputs

- [x] closes #42229
- [x] tests added / passed
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [x] whatsnew entry - Updated the return type section of to_datetime to include list-like mixed timezone inputs
