Update flake8-docstrings minimum version to 1.5.0

[mattsb42-aws]

We can temporarily work around this by pinning to pydocstyle < 4.0.0, but we need to figure out what's going on here and what path forward we want to take.

[mattsb42-aws]

I can't seem to replicate this issue anymore, and I neglected to actually document what the error was. :/

I suspect the this was the issue[1], though. I feel like I've seen another error, but that might be unrelated.

I'm going to change this to bumping our minimum versions of flake8-docstrings to 1.5.0.

[1] https://gitlab.com/pycqa/flake8-docstrings/issues/36