Resolve type issue that arose from merge

synapse/rest/client/register.py

@@ -763,7 +763,10 @@ async def _create_registration_details(
         Returns:
              dictionary for response from /register
         """
-        result = {"user_id": user_id, "home_server": self.hs.hostname}
+        result: Dict[str, Union[str, int]] = {
+            "user_id": user_id,
+            "home_server": self.hs.hostname,
+        }
         if not params.get("inhibit_login", False):
             device_id = params.get("device_id")
             initial_display_name = params.get("initial_device_display_name")