[CombinerHelper] Fix gcc warning [NFC]

Without the fix gcc complains with
 ../lib/CodeGen/GlobalISel/CombinerHelper.cpp:1652:52: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
  1652 |          SrcDef->getOpcode() == TargetOpcode::G_OR && "Unexpected op");
       |          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~