Enable PYI059 (#15399)

Author: srittau

pyproject.toml

@@ -106,7 +106,7 @@ select = [
     "PYI044", # `from __future__ import annotations` has no effect in stub files, since type checkers automatically treat stubs as having those semantics
     "PYI055", # Multiple `type[T]` usages in a union. Combine them into one, e.g., `type[{union_str}]`.
     "PYI058", # Use `{return_type}` as the return value for simple `{method}` methods
-    # "PYI059", # TODO: Add when dropping Python 3.9 support
+    "PYI059", # Checks for classes inheriting from typing.Generic[] where Generic[] is not the last base class in the bases tuple
     "PYI061", # Use `None` rather than `Literal[None]`
     "PYI062", # Duplicate literal member `{}`
     "PYI064", # `Final[Literal[{literal}]]` can be replaced with a bare Final