Pin black importlib metadata dependencies

[woutervanoorschot]

There is no 0.x next release branch and as such I have created this PR to dev (in conflict with the contributing guidelines)

It fixes errors in the pre commit linting caused by an exception in black 22.1.0 and a deprecation from importlib-metadata >= 5.

Hopefully this is useful and can be merged.

[woutervanoorschot]

I believe the errors are caused by deprecations in werkzeug #1963:

Merge all request and response wrapper mixin code into single Request and Response classes. Using the mixin classes is no longer necessary and will show a deprecation warning. Checking isinstance or issubclass against BaseRequest and BaseResponse will show a deprecation warning and check against Request or Response instead.

The code in https://github.com/marshmallow-code/flask-marshmallow/blob/dev/tests/test_sqla.py should be updated from checking BaseResponse to Response.

Also python 3.6 will be deprecated by these fixes, but python 3.6 is EOL anyway. It should be a new major version

[woutervanoorschot]

The changes have become a bit bigger in scope to fix all the errors in the pipelines and pre-commit checks. Hopefully it is still readable for a reviewer.

My project depends on the flask-marshmallow package and hopefully this can help keep the development going.