REGR: object column repr not respecting float format
- [x] closes #40024
- [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

This is a regression caused by #38759
Thanks @mzeitlin11  @meeseeksdev backport 1.2.x