Don't check whether a 3pid is allowed to register during password reset

This endpoint should only deal with emails that have already been approved, and
are attached with user's account. There's no need to re-check them here.

synapse/rest/client/v2_alpha/account.py

@@ -96,13 +96,6 @@ async def on_POST(self, request):
         send_attempt = body["send_attempt"]
         next_link = body.get("next_link")  # Optional param
 
-        if not check_3pid_allowed(self.hs, "email", email):
-            raise SynapseError(
-                403,
-                "Your email domain is not authorized on this server",
-                Codes.THREEPID_DENIED,
-            )
-
         # Raise if the provided next_link value isn't valid
         assert_valid_next_link(self.hs, next_link)