Don't create a GLib main loop.

In the Qt Wireshark, the main loop is a Qt main loop; no need for a GLib
one.

Change-Id: I65378eb9a73d145ef60389e5e02a128e2321c403
Reviewed-on: https://code.wireshark.org/review/8721
Reviewed-by: Guy Harris <guy@alum.mit.edu>

wireshark-qt.cpp

@@ -1380,7 +1380,6 @@ DIAG_ON(cast-qual)
     }
 #endif /* HAVE_LIBPCAP */
 
-    g_main_loop_new(NULL, FALSE);
     return wsApp->exec();
 }