LArCondTools: Fix cppcheck warning.

Don't use string::find to test the start of a string.

LArCalorimeter/LArCondTools/src/FixLArElecCalib.cxx

 /*
-  Copyright (C) 2002-2022 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2024 CERN for the benefit of the ATLAS collaboration
 */
 
 /**
@@ -828,7 +828,7 @@ StatusCode FixLArElecCalib::fix5 ATLAS_NOT_THREAD_SAFE (const LArOnOffIdMapping
      while ( infile>>str_id >>vol>>noise_p>>noise_h>>noise_m>>noise_l )
      {
        const char* ch_id = str_id.c_str();
-       if(str_id.find('A')!=0){
+       if(ch_id[0] != 'A') {
 	 ATH_MSG_DEBUG(" skipping string"<<str_id);
          continue;  
        }