LArClusterCellMonAlg : fix clang warnings
fixes
In file included from /build/atnight/localbuilds/nightlies/Athena/master/athena/Calorimeter/CaloMonitoring/src/LArClusterCellMonAlg.cxx:5:
/build/atnight/localbuilds/nightlies/Athena/master/athena/Calorimeter/CaloMonitoring/src/LArClusterCellMonAlg.h:73:44: warning: private field 'm_layerEnumtoPartitionEnum' is not used [-Wunused-private-field]
const std::array<PartitionEnum,MAXLAYER> m_layerEnumtoPartitionEnum{{