Remove a racy assert

With the recent changes where HSH_Unbusy/HSH_Fail is called after
ObjSetState, this assert becomes racy. Remove the assert.

bin/varnishd/cache/cache_fetch.c

@@ -980,9 +980,6 @@ VBF_Fetch(struct worker *wrk, struct req *req, struct objcore *oc,
 			(void)VRB_Ignore(req);
 		} else {
 			ObjWaitState(oc, BOS_STREAM);
-			if (oc->boc->state == BOS_FAILED) {
-				AN((oc->flags & OC_F_FAILED));
-			}
 		}
 	}
 	AZ(bo);