Fix typo in account_threepid_delegates config (#6028)

changelog.d/6028.feature

+Replace `trust_identity_server_for_password_resets` config option with `account_threepid_delegates`.

docs/sample_config.yaml

@@ -938,7 +938,7 @@ uploads_path: "DATADIR/uploads"
 # https://matrix.org/docs/spec/identity_service/latest
 #
 account_threepid_delegates:
-    #email: https://example.com     # Delegate email sending to matrix.org
+    #email: https://example.com     # Delegate email sending to example.org
     #msisdn: http://localhost:8090  # Delegate SMS sending to this local process
 
 # Users who register on this homeserver will automatically be joined

synapse/config/registration.py

@@ -294,7 +294,7 @@ class RegistrationConfig(Config):
         # https://matrix.org/docs/spec/identity_service/latest
         #
         account_threepid_delegates:
-            #email: https://example.com     # Delegate email sending to matrix.org
+            #email: https://example.com     # Delegate email sending to example.org
             #msisdn: http://localhost:8090  # Delegate SMS sending to this local process
 
         # Users who register on this homeserver will automatically be joined