fix flake8 and black

[hsirkar]

develop fails because of black issues:

would reformat /home/rakrish/pipit/pipit/util/cct.py
would reformat /home/rakrish/pipit/pipit/readers/otf2_reader.py

Oh no! 💥 💔 💥

and flake8 issues;

./pipit/readers/projections_reader.py:516:22: N806 variable 'numPEs' in function should be lowercase
./pipit/readers/projections_reader.py:517:22: N806 variable 'destPEs' in function should be lowercase
./pipit/trace.py:600:51: N803 argument name 'MPI_events' should be lowercase
./pipit/trace.py:614:50: N803 argument name 'MPI_events' should be lowercase

This PR fixes them.