[mle] fix incorrect StatusTlv when processing Child Update Response (#7956)

This commit fixes `MleRouter::HandleChildUpdateResponse()` to use the
MLE `StatusTlv` instead of `ThreadStatusTlv` when parsing a received
MLE Child Update Response (from a child).

src/core/thread/mle_router.cpp

@@ -2771,7 +2771,7 @@ void MleRouter::HandleChildUpdateResponse(RxInfo &aRxInfo)
     }
 
     // Status
-    switch (Tlv::Find<ThreadStatusTlv>(aRxInfo.mMessage, status))
+    switch (Tlv::Find<StatusTlv>(aRxInfo.mMessage, status))
     {
     case kErrorNone:
         VerifyOrExit(status != StatusTlv::kError, RemoveNeighbor(*child));