Fix bug where a :class:`typing.Protocol` class that had one or more non-callable members would raise :exc:`TypeError` when :func:`issubclass` was called against it, even if it defined a custom ``__subclasshook__`` method. The behaviour in Python 3.11 and lower -- which has now been restored -- was not to raise :exc:`TypeError` in these situations if a custom ``__subclasshook__`` method was defined. Patch by Alex Waygood.