I temporarily pinned two packages that will require more significant
updates (webargs in requirements and prospector in requirements-dev).
Other than those, everything seemed to upgrade cleanly, except for an
issue with mypy that needed a "type: ignore" comment to circumvent.

Note that there is currently an issue with Salt's pip module being
unable to handle comments in a requirements file that include "-r", so I
had to manually edit the two .txt files after using pip-tools to remove
all lines with "via -r" comments in them. I've commented about this in
an issue on Salt's repo here:
https://github.com/saltstack/salt/issues/56514#issuecomment-665947887