Remove unused pylint suppressions

pylint is not used since bb5b1a07. The pyflakes cleanup mentioned in that
commit has not been done, but given that this project is no longer being
actively developed I don't think it's worth spending time doing it.

Leaving the pylint suppressions causes confusion because it leads people
to think that we are still using pylint.

Change-Id: If7d9f280a0f408c780f15915ffdb80579ae21f69