Don't check whether a 3pid is allowed to register during password reset (#8414)

* 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.

* Changelog

changelog.d/8414.bugfix

@@ -0,0 +1 @@
+Remove unnecessary 3PID registration check when resetting password via an email address. Bug introduced in v0.34.0rc2.

synapse/rest/client/v2_alpha/account.py

@@ -96,13 +96,6 @@ class EmailPasswordRequestTokenRestServlet(RestServlet):
         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,
-            )
-
         if next_link:
             # Raise if the provided next_link value isn't valid
             assert_valid_next_link(self.hs, next_link)