[NFC][MC] Removed unused switch case in emitCATTR (#152907)

The switch statement `switch (Rmode)` is in an if-block that checks if
`Rmode != GOFF::ESD_RMODE_None` making the `case GOFF::ESD_RMODE_None:`
unnecessary.

Author: abhishek-kaushik22

llvm/lib/MC/MCAsmInfoGOFF.cpp

@@ -71,8 +71,6 @@ static void emitCATTR(raw_ostream &OS, StringRef Name, GOFF::ESDRmode Rmode,
     case GOFF::ESD_RMODE_64:
       OS << "64";
       break;
-    case GOFF::ESD_RMODE_None:
-      break;
     }
     OS << ')';
   }