docs: Remove obselete appendix about parsing cli argumnets

It's a bad idea trying to mix the Options from GStramer and
GTK, in addition with cli argument being a bit wonky thing for
GUI applications in general. In the rare, now, occasion
that an application wants to parse arguments, its preferable
to parse them manually and use library apis afterwards
rather than trying to combine the option groups and hope it
works.

In addition, applications should be opening files using
`g_application_open` instead of parsing random arguments.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/4788>

subprojects/gst-docs/markdown/application-development/appendix/integration.md

@@ -42,87 +42,6 @@ Juicer](https://wiki.gnome.org/Apps/SoundJuicer).
 Most of these GNOME applications make use of some specific techniques to
 integrate as closely as possible with the GNOME desktop:
 
-  - GNOME applications usually call `gtk_init ()` to parse command-line
-    options and initialize GTK. GStreamer applications would normally
-    call `gst_init ()` to do the same for GStreamer. This would mean
-    that only one of the two can parse command-line options. To work
-    around this issue, GStreamer can provide a GLib `GOptionGroup` which
-    can be passed to `gnome_program_init ()`. The following example
-    requires GTK 2.6 or newer (previous GTK versions do not support
-    command line parsing via GOption yet)
-
-    ``` c
-    #include <gtk/gtk.h>
-    #include <gst/gst.h>
-
-    static gchar **cmd_filenames = NULL;
-
-    static GOptionEntries cmd_options[] = {
-      /* here you can add command line options for your application. Check
-       * the GOption section in the GLib API reference for a more elaborate
-       * example of how to add your own command line options here */
-
-      /* at the end we have a special option that collects all remaining
-       * command line arguments (like filenames) for us. If you don't
-       * need this, you can safely remove it */
-      { G_OPTION_REMAINING, 0, 0, G_OPTION_ARG_FILENAME_ARRAY, &cmd_filenames,
-        "Special option that collects any remaining arguments for us" },
-
-      /* mark the end of the options array with a NULL option */
-      { NULL, }
-    };
-
-    /* this should usually be defined in your config.h */
-    #define VERSION "0.0.1"
-
-    gint
-    main (gint argc, gchar **argv)
-    {
-      GOptionContext *context;
-      GOptionGroup *gstreamer_group, *gtk_group;
-      GError *err = NULL;
-
-      context = g_option_context_new ("gtk-demo-app");
-
-      /* get command line options from GStreamer and add them to the group */
-      gstreamer_group = gst_init_get_option_group ();
-      g_option_context_add_group (context, gstreamer_group);
-      gtk_group = gtk_get_option_group (TRUE);
-      g_option_context_add_group (context, gtk_group);
-
-      /* add our own options. If you are using gettext for translation of your
-       * strings, use GETTEXT_PACKAGE here instead of NULL */
-      g_option_context_add_main_entries (context, cmd_options, NULL);
-
-      /* now parse the commandline options, note that this already
-       * calls gtk_init() and gst_init() */
-      if (!g_option_context_parse (ctx, &argc, &argv, &err)) {
-        g_print ("Error initializing: %s\n", err->message);
-        g_clear_error (&err);
-        g_option_context_free (ctx);
-        exit (1);
-      }
-      g_option_context_free (ctx);
-
-      /* any filenames we got passed on the command line? parse them! */
-      if (cmd_filenames != NULL) {
-        guint i, num;
-
-        num = g_strv_length (cmd_filenames);
-        for (i = 0; i < num; ++i) {
-          /* do something with the filename ... */
-          g_print ("Adding to play queue: %s\n", cmd_filenames[i]);
-        }
-
-        g_strfreev (cmd_filenames);
-        cmd_filenames = NULL;
-      }
-
-    [..]
-
-    }
-    ```
-
   - GNOME uses Pulseaudio for audio, use the pulsesrc and pulsesink
     elements to have access to all the features.