Update condition.h

Missing default Return statement

src/shader_recompiler/ir/condition.h

@@ -37,6 +37,8 @@ constexpr std::string_view NameOf(Condition condition) {
         return "Execz";
     case Condition::Execnz:
         return "Execnz";
+    default:
+        return "Invalid";
     }
 }