[REVERT] Add in metrics counter to prove this gets hit

synapse/storage/databases/main/event_federation.py

@@ -73,6 +73,9 @@
     "The number of events in the inbound federation staging that have been "
     "pruned due to the queue getting too long",
 )
+excluded_zeros_from_auth_chain_query = Counter(
+    "synapse_temp_auth_chain_zero_sequence", ""
+)
 
 logger = logging.getLogger(__name__)
 
@@ -305,6 +308,8 @@ def _get_auth_chain_ids_using_cover_index_txn(
             max_sequence_result = max(seq_no - 1, chains.get(chain_id, 0))
             if max_sequence_result > 0:
                 chains[chain_id] = max_sequence_result
+            else:
+                excluded_zeros_from_auth_chain_query.inc()
 
         # Now for each chain we figure out the maximum sequence number reachable
         # from *any* event ID. Events with a sequence less than that are in the