a11y: set again NO_AT_BRIDGE=1 before calling meta_init()

It was removed on commit
70099872ab
because it was thought to not be needed anymore.

https://bugzilla.gnome.org/show_bug.cgi?id=736821

src/main.c

@@ -424,7 +424,10 @@ main (int argc, char **argv)
   meta_set_wm_name (WM_NAME);
   meta_set_gnome_wm_keybindings (GNOME_WM_KEYBINDINGS);
 
+  /* Prevent meta_init() from causing gtk to load the atk-bridge*/
+  g_setenv ("NO_AT_BRIDGE", "1", TRUE);
   meta_init ();
+  g_unsetenv ("NO_AT_BRIDGE");
 
   /* FIXME: Add gjs API to set this stuff and don't depend on the
    * environment.  These propagate to child processes.