Reenable Windows as a required CI check

[bpkroth]

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I've temporarily marked the Windows CI test as not required since there's something odd going on with it.

It's complaining about the same issue already addressed in #757, but somewhat intermittently.

ERROR mlos_bench/mlos_bench/tests/tunables/tunable_to_configspace_test.py - ValueError: numpy.dtype size changed, may indicate binary incompatibility. Expected 96 from C header, got 88 from PyObject
ERROR mlos_bench/mlos_bench/tests/tunables/tunable_to_configspace_distr_test.py - ValueError: numpy.dtype size changed, may indicate binary incompatibility. Expected 96 from C header, got 88 from PyObject
ERROR mlos_bench/mlos_bench/tests/tunables/tunable_to_configspace_test.py - ValueError: numpy.dtype size changed, may indicate binary incompatibility. Expected 96 from C header, got 88 from PyObject
ERROR mlos_viz/mlos_viz/tests - ValueError: numpy.dtype size changed, may indicate binary incompatibility. Expected 96 from C header, got 88 from PyObject
ERROR mlos_viz/mlos_viz/tests - ValueError: numpy.dtype size changed, may indicate binary incompatibility. Expected 96 from C header, got 88 from PyObject

However, it reports that the older version of numpy is correctly being installed.

There are at least two PRs that don't touch any Windows checks that are currently failing due to this so we'll just manually inspect and keep it as optional for the moment.