Exclude generated session_pb2.py from flake/black

Author: jagerman

.flake8

@@ -2,4 +2,4 @@
 per-file-ignores = __init__.py:F401 sogs/session_pb2.py:E501
 max-line-length = 100
 extend-ignore = E203  # See https://github.com/psf/black/issues/315
-exclude=sogs/config.py
+exclude=sogs/config.py,sogs/session_pb2.py

pyproject.toml

@@ -4,3 +4,4 @@ skip-string-normalization = true
 skip-magic-trailing-comma = true
 target-version = ['py38']
 include = '\.py$'
+extend-exclude = 'sogs/session_pb2.py'