CI: Remove 'env' from pytest.ini

[WarrenWeckesser]

No description provided.

[WarrenWeckesser]

This fixes the error that we've been getting with pytest 6.0 in recent PRs.

The cancelled Azure run, "scipy.scipy (Windows Python36-32bit-fast)", is weird. It appears to be a leftover from a previous run of the test suite. I closed and opened the PR, and the tests ran again, but that cancelled item remained in the list. Note that there is another entry for "scipy.scipy (Windows Python36-32bit-fast)" that has passed.

I haven't figured out the cause of the Travis CI failure for the platform AMD64 / xenial / "Wheel, Optimised, GCC 4.8". The end of the log says

pytest.PytestConfigWarning: assertions not in test modules or plugins will be ignored because assert statements are not executed by the underlying Python interpreter (are you using python -O?)

That test runs with the environment variable PYTHONOPTIMIZE=2.

[WarrenWeckesser]

The Travis CI failure on AMD64 / xenial / "Wheel, Optimised, GCC 4.8" has occurred on other recent PRs (e.g. #12889 and #12899), so it is not related to this PR. I'm moving this PR out of "draft" mode, as it fixes multiple failures being caused by a change in python 6.0. We can deal with the remaining failure in a separate PR.

[sethtroisi]

@WarrenWeckesser Merging so we can unblock large number of other PRs.

It does seem like we should potentially add PYTHONHASHSEED=0 back using some other mechanism

[tylerjereddy]

This needs to be backported to gh-12906 based on CI fails there, so proceeding with that