modified ERR log to NOTICE log for FDB notification failure after VLAN delete (sonic-net#1595)

the VLAN is already removed and we are receiving a FLUSH notification for the same,
it should be treated as a warning and not an error.

Co-authored-by: Madhan Babu <madhan@arc-build-server.mtr.labs.mlnx>

Author: madhanmellanox

orchagent/fdborch.cpp

@@ -184,7 +184,7 @@ void FdbOrch::update(sai_fdb_event_t        type,
 
         if (!m_portsOrch->getPort(entry->bv_id, vlan))
         {
-            SWSS_LOG_ERROR("FdbOrch LEARN notification: Failed to locate vlan port from bv_id 0x%" PRIx64, entry->bv_id);
+            SWSS_LOG_NOTICE("FdbOrch LEARN notification: Failed to locate vlan port from bv_id 0x%" PRIx64, entry->bv_id);
             return;
         }