Fixed more SS03 errors
Fixed SS03 errors in the docstrings for `pandas.tseries.frequencies.to_offset`; `pandas.Int64Index`; `pandas.UInt64Index`; `pandas.Float64Index`; `pandas.IntervalIndex`; `pandas.plotting.plot_params`; `pandas.io.formats.style.Styler.loader`.

- [x] xref #29315
- [ ] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

This is part of the docstring errors in #27977.
