Revert "REF: isinstance(x, int) -> is_integer(x)"
Reverts pandas-dev/pandas#46119

It looks like this can be auto reverted. (won't know till ci has run)

@attack68 if we revert this, we could redo and add a regression test for #46384 to address https://github.com/pandas-dev/pandas/pull/46119#issuecomment-1049069600, add a release note for the bugfix and maybe backport to 1.4.x. wdyt?

I think should probably reopen #46384 and add a test to close that issue off anyway.
closing in favor of #46501 https://github.com/pandas-dev/pandas/pull/46501#issuecomment-1080836198