Merge etc/pip/components/mypy.req with etc/pip/components/lint.req

For some reason the python requirements for linting are broken into 2 files. One for general requirements and the other for mypy. My guess is that this was due to mypy not being able to run in python 2. But now that python 3 is used everywhere, there doesn't seem to be any other reason to prevent us from merging the two requirements files.