[network-data] remove ClearResubmitDelayTimer() in UpdateRloc() (#4485)

`UpdateRloc()`, which happens before checking network data consistence,
should not `ClearResubmitDelayTimer()` to guarantee the DATA_RESUBMIT_DELAY
before resending when there is inconsistence.

src/core/thread/network_data_local.cpp

@@ -344,8 +344,6 @@ void Local::UpdateRloc(void)
             break;
         }
     }
-
-    ClearResubmitDelayTimer();
 }
 
 otError Local::SendServerDataNotification(void)