Remove some extraneous # noqa comments

This was partially automated with https://github.com/asottile/yesqa

_with a few caveats_:
- it was run under python2 (chosen arbitrarily, when run under python3 other
  things were changed)
- I used `git checkout -p` to revert the removal of `noqa` comments from
  `cmp()` lines.

src/_pytest/compat.py

@@ -41,8 +41,8 @@ PY36 = sys.version_info[:2] >= (3, 6)
 MODULE_NOT_FOUND_ERROR = "ModuleNotFoundError" if PY36 else "ImportError"
 
 if _PY3:
-    from collections.abc import MutableMapping as MappingMixin  # noqa
-    from collections.abc import Mapping, Sequence  # noqa
+    from collections.abc import MutableMapping as MappingMixin
+    from collections.abc import Mapping, Sequence
 else:
     # those raise DeprecationWarnings in Python >=3.7
     from collections import MutableMapping as MappingMixin  # noqa

src/_pytest/config/__init__.py

@@ -71,7 +71,7 @@ def main(args=None, plugins=None):
         return 4
 
 
-class cmdline(object):  # NOQA compatibility namespace
+class cmdline(object):  # compatibility namespace
     main = staticmethod(main)