Wifi (macOS): fix build on old OS version

src/detection/wifi/wifi_apple.m

@@ -297,7 +297,7 @@ @interface CWInterface()
         {
             case kCWChannelBand2GHz: item->conn.frequency = 2400; break;
             case kCWChannelBand5GHz: item->conn.frequency = 5000; break;
-            case kCWChannelBand6GHz: item->conn.frequency = 6000; break;
+            case 3 /*kCWChannelBand6GHz*/: item->conn.frequency = 6000; break;
             default: item->conn.frequency = 0; break;
         }
     }