Revert "Backport PR #39526 on branch 1.2.x (CI: pin numpy for CI / Checks github action)"
Reverts pandas-dev/pandas#39529

will be merging this just prior to tagging 1.2.2 see https://github.com/pandas-dev/pandas/issues/39513#issuecomment-771006563 and then re-appling after release so that ci on 12.x is green