Set follow-imports to normal (default)

With follow-imports set to skip, behavior between running mypy on the
whole module and just on single files (e.g. used in pre-commit) is
different. This allows mypy to follow imported modules which would
otherwise be ignored, including other submodules of gama.

mypy.ini

@@ -18,7 +18,6 @@ warn_unused_configs=True
 # Probably want to turn back on later:
 #no_implicit_optional
 ignore_missing_imports=True
-follow_imports=skip
 
 # Following configuration are default, but made explicit:
 warn_no_return=True