Avoid useless check for GTK_CHECK_VERSION

Just use it inside the existing check for GTK itself.

No real changes.

src/unix/utilsx11.cpp

@@ -48,13 +48,11 @@
 #endif
 GdkWindow* wxGetTopLevelGDK();
 GtkWidget* wxGetTopLevelGTK();
-#endif
 
-#ifdef GTK_CHECK_VERSION
 #if GTK_CHECK_VERSION(3,4,0)
 #define wxHAS_GETKEYSTATE_GTK
 #endif //GTK+ 3.4
-#endif
+#endif // GTK
 
 // Only X11 backend is supported for wxGTK here (GTK < 2 has no others)
 #if !defined(__WXGTK__) || \