Fix clang warning in MuonReadoutGeomCnvAlg
Fix the following warning:
athena/MuonSpectrometer/MuonPhaseII/MuonCnv/MuonGeometryCnv/src/MuonReadoutGeomCnvAlg.cxx:198:20: error: expression with side effects will be evaluated despite being used as an operand to 'typeid' [-Werror,-Wpotentially-evaluated-expression]
198 | if (typeid(*childVol) == typeid(GeoFullPhysVol)) {
| ^
1 error generated.