www-client/firefox: update default setting

profiles/templates/3.6/6_ac_desktop_profile/2-user/www-client/firefox-68/calculate.default/prefs.js

@@ -105,7 +105,6 @@ user_pref("javascript.options.asyncstack", true);
 user_pref("media.autoplay.default", 0);
 user_pref("media.eme.apiVisible", false);
 user_pref("media.getusermedia.screensharing.allowed_domains", "");
-user_pref("media.getusermedia.screensharing.enabled", false);
 user_pref("media.navigator.enabled", false);
 user_pref("media.video_stats.enabled", false);
 user_pref("memory.free_dirty_pages", true);