One other type fix

Signed-off-by: BryceGattis <brycegattis@yahoo.com>

src/rez/plugin_managers.py

@@ -340,7 +340,7 @@ def _get_plugin_type(self, plugin_type: str) -> RezPluginType:
             raise RezPluginError("Unrecognised plugin type: '%s'"
                                  % plugin_type)
 
-    def register_plugin_type(self, type_class: RezPluginType):
+    def register_plugin_type(self, type_class: Type[RezPluginType]):
         if not issubclass(type_class, RezPluginType):
             raise TypeError("'type_class' must be a RezPluginType sub class")
         if type_class.type_name is None: