GTK4: gtk_init_check() does not take args

In GTK+4 gtk_init_check() takes no arguments, while in GTK+3 you could
pass argc/argv.

I'm not quite sure how to pass any arguments to GTK+4, so just call
gtk_init_check() in GTK+4.

src/gtk/app.cpp

@@ -361,6 +361,8 @@ bool wxApp::Initialize(int& argc_, wxChar **argv_)
 #ifdef __WXGPE__
     init_result = true;  // is there a _check() version of this?
     gpe_application_init( &argcGTK, &argvGTK );
+#elif defined(__WXGTK4__)
+    init_result = gtk_init_check() != 0;
 #else
     init_result = gtk_init_check( &argcGTK, &argvGTK ) != 0;
 #endif