WebDriver: Pass --enable-qt-networking when launching Ladybird

Using Qt networking when running web platform tests improves
performance significantly. The time to run the subset of tests we run
on CI drops from 47.2 seconds to 8.2 seconds on my machine.

Ladybird/WebDriver/main.cpp

@@ -47,6 +47,7 @@ static ErrorOr<pid_t> launch_browser(ByteString const& socket_path)
 
     arguments.append("--allow-popups");
     arguments.append("--force-new-process");
+    arguments.append("--enable-qt-networking");
 
     arguments.append("about:blank");