CI: add pre-commit action, include pyupgrade
xref this comment https://github.com/pandas-dev/pandas/issues/36426#issuecomment-694238629 by @TomAugspurger 

> I would recommend running the linting commands on CI through pre-commit. That way the versions in .pre-commit-config.yaml are used everywhere.

So, this PR does that.

It also adds pyupgrade as a pre-commit hook (xref #36450 ) and removes some unnecessary configurations from the `.pre-commit-config.yaml` file (all of these hooks already specify `language: python`, see e.g. https://github.com/psf/black/blob/master/.pre-commit-hooks.yaml )

TODO
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update https://pandas.pydata.org/docs/development/contributing.html#code-standards (thanks Ali!)