lint: Prevent self: Any annotations.

We should omit these for mypy.  For most class definitions,
mypy doesn't need `Any`, and it provides no real useful info.

For clever monkeypatches, you should provide a more specific
type than `Any`.

tools/linter_lib/custom_check.py

@@ -264,6 +264,10 @@ def build_custom_checkers(by_lang):
          'description': 'Missing space around "%"',
          'good_lines': ["'%s' % ('foo')", "'%s' % (foo)"],
          'bad_lines': ["'%s'%('foo')", "'%s'%(foo)"]},
+        {'pattern': 'self: Any',
+         'description': 'you can omit Any annotation for self',
+         'good_lines': ['def foo (self):'],
+         'bad_lines': ['def foo(self: Any):']},
         # This rule is constructed with + to avoid triggering on itself
         {'pattern': " =" + '[^ =>~"]',
          'description': 'Missing whitespace after "="',