py3.9 pinning causes CI to fail

[fjetter]

With the latest releases we seem to run into compatibilities for some platform connected to s3fs/fsspec
It appears the pinning in s3fs is a bit too strict

  The conflict is caused by:
      The user requested fsspec 2021.6.1 (from git+https://github.com/intake/filesystem_spec)
      dask 2021.6.2+1.g38f8de4e depends on fsspec>=0.6.0
      s3fs 2021.6.0+13.g9416184 depends on fsspec==2021.06.0

cc @martindurant

#4951 - https://github.com/dask/distributed/pull/4951/checks?check_run_id=2893242426

[martindurant]

s3fs and gcsfs coming today, they are always released together now.

[martindurant]

on pypi now, this can probably be closed.

[fjetter]

I can confirm this issue has been resolved. Thanks @martindurant !