Addressed minor errors caught by pyright in stdlib stubs (#4880)

* Removed unused import symbols from stdlib stubs and fixed a few other errors detected by pyright. I did a similar pass several months ago; these were introduced since then.

* Added a few missing types and type arguments. Removed unused import statement. Removed default values that caused overloads to have overlapping signatures.

Co-authored-by: Eric Traut <erictr@microsoft.com>

stdlib/3/unittest/mock.pyi

@@ -387,7 +387,7 @@ if sys.version_info >= (3, 8):
         def assert_any_await(self, *args: Any, **kwargs: Any) -> None: ...
         def assert_has_awaits(self, calls: _CallList, any_order: bool = ...) -> None: ...
         def assert_not_awaited(self) -> None: ...
-        def reset_mock(self, *args, **kwargs) -> None: ...
+        def reset_mock(self, *args: Any, **kwargs: Any) -> None: ...
         await_count: int
         await_args: Optional[_Call]
         await_args_list: _CallList