enable warn_unreachable = True for mypyc and all other files as well

Author: wyattscarpenter

mypy_self_check.ini

@@ -13,7 +13,4 @@ exclude = mypy/typeshed/|mypyc/test-data/|mypyc/lib-rt/
 enable_error_code = ignore-without-code,redundant-expr
 enable_incomplete_feature = PreciseTupleTypes
 show_error_code_links = True
-
-[mypy-mypy.*]
-# TODO: enable for `mypyc` and other files as well
 warn_unreachable = True