Fix running with GTK 4.2

src/main.c

@@ -73,7 +73,7 @@ int
 main (int    argc,
       char **argv)
 {
-    GtkApplication *app = gtk_application_new ("uk.me.bcowan.Rugby",
+    GtkApplication *app = gtk_application_new ("uk.me.bcowan.rugby",
                                                G_APPLICATION_FLAGS_NONE);
 
     g_signal_connect (app, "startup",