(doc update): Change Tweak Message For Checkpointing Sanity Check Fai…

…lure facebook#1734

See: facebook#1734 facebook#1734

hasher-matcher-actioner/src/OpenMediaMatch/storage/postgres/impl.py

@@ -341,7 +341,7 @@ def exchange_commit_fetch(
         existing_checkpoint = cfg.as_checkpoint(self.exchange_apis_get_installed())
         assert (
             existing_checkpoint == old_checkpoint
-        ), "Old checkpoint doesn't match, race condition?"
+        ), "Checkpoint has changed since fetch started - multiple fetch processes may be running simultaneously."
 
         api_cls = self.exchange_apis_get_installed().get(collab.api)
         assert api_cls is not None, "Invalid API cls?"