Revert "Merge pull request #3431 from matrix-org/rav/erasure_visibility"

This reverts commit ce0d911156, reversing
changes made to b4a5d767a9.

synapse/handlers/federation.py

@@ -495,20 +495,7 @@ class FederationHandler(BaseHandler):
             for e_id, key_to_eid in event_to_state_ids.iteritems()
         }
 
-        erased_senders = yield self.store.are_users_erased(
-            e.sender for e in events,
-        )
-
         def redact_disallowed(event, state):
-            # if the sender has been gdpr17ed, always return a redacted
-            # copy of the event.
-            if erased_senders[event.sender]:
-                logger.info(
-                    "Sender of %s has been erased, redacting",
-                    event.event_id,
-                )
-                return prune_event(event)
-
             if not state:
                 return event