unpin pip 20.2 again (#4656)
unpin pip 20.2 again (#4656)

* unpin pip 20.2 again

* [test-upstream] trigger upstream-dev

* [test-upstream] trigger upstream-dev

* [test-upstream] [skip-ci]

Co-authored-by: Keewis <39a065c0f814f810a499b803da99b94c24527abc@posteo.de>
pydata/xarray,markelg/xray,pydata/xarray,jhamman/xarray,pydata/xarray,markelg/xray,markelg/xray,jhamman/xarray,jhamman/xarray