Remove unneeded cerr messages in MetaCont

Control/AthenaKernel/AthenaKernel/MetaCont.h

@@ -192,12 +192,14 @@ bool MetaCont<T>::find(const SourceID& it, T*& t) const {
     t=itr->second;
     return true;
   }
+/*
   else {
     std::cerr << "SID=" << it << " not found" << std::endl;
     for (const auto& elt : m_metaSet) {
       std::cerr << "Container has SID=" << elt.first << std::endl;
     }
   }
+*/
 
   return false;
 }