docs: Move the GCompletion SECTION

Move it to the struct docs.

Signed-off-by: Philip Withnall <pwithnall@gnome.org>

Helps: #3037

glib/deprecated/gcompletion.c

@@ -43,34 +43,6 @@
 
 #include <string.h>
 
-/**
- * SECTION:completion
- * @title: Automatic String Completion
- * @short_description: support for automatic completion using a group
- *                     of target strings
- *
- * #GCompletion provides support for automatic completion of a string
- * using any group of target strings. It is typically used for file
- * name completion as is common in many UNIX shells.
- *
- * A #GCompletion is created using g_completion_new(). Target items are
- * added and removed with g_completion_add_items(),
- * g_completion_remove_items() and g_completion_clear_items(). A
- * completion attempt is requested with g_completion_complete() or
- * g_completion_complete_utf8(). When no longer needed, the
- * #GCompletion is freed with g_completion_free().
- *
- * Items in the completion can be simple strings (e.g. filenames), or
- * pointers to arbitrary data structures. If data structures are used
- * you must provide a #GCompletionFunc in g_completion_new(), which
- * retrieves the item's string from the data structure. You can change
- * the way in which strings are compared by setting a different
- * #GCompletionStrncmpFunc in g_completion_set_compare().
- *
- * GCompletion has been marked as deprecated, since this API is rarely
- * used and not very actively maintained.
- **/
-
 /**
  * GCompletion:
  * @items: list of target items (strings or data structures).
@@ -82,7 +54,29 @@
  * @strncmp_func: The function to use when comparing strings.  Use
  *                g_completion_set_compare() to modify this function.
  *
- * The data structure used for automatic completion.
+ * `GCompletion` provides support for automatic completion of a string
+ * using any group of target strings. It is typically used for file
+ * name completion as is common in many UNIX shells.
+ *
+ * A `GCompletion` is created using [func@GLib.Completion.new]. Target items are
+ * added and removed with [method@GLib.Completion.add_items],
+ * [method@GLib.Completion.remove_items] and
+ * [method@GLib.Completion.clear_items]. A completion attempt is requested with
+ * [method@GLib.Completion.complete] or [method@GLib.Completion.complete_utf8].
+ * When no longer needed, the `GCompletion` is freed with
+ * [method@GLib.Completion.free].
+ *
+ * Items in the completion can be simple strings (e.g. filenames), or
+ * pointers to arbitrary data structures. If data structures are used
+ * you must provide a [type@GLib.CompletionFunc] in [func@GLib.Completion.new],
+ * which retrieves the item’s string from the data structure. You can change
+ * the way in which strings are compared by setting a different
+ * [type@GLib.CompletionStrncmpFunc] in [method@GLib.Completion.set_compare].
+ *
+ * `GCompletion` has been marked as deprecated, since this API is rarely
+ * used and not very actively maintained.
+ *
+ * Deprecated: 2.26: Rarely used API
  **/
 
 /**
@@ -94,6 +88,7 @@
  * This is used when you use data structures as #GCompletion items.
  *
  * Returns: the string corresponding to the item.
+ * Deprecated: 2.26: Rarely used API
  **/
 
 /**
@@ -110,6 +105,7 @@
  *          the first @n bytes of @s1 is found, respectively, to be
  *          less than, to match, or to be greater than the first @n
  *          bytes of @s2.
+ * Deprecated: 2.26: Rarely used API
  **/
 
 static void completion_check_cache (GCompletion* cmp,
@@ -124,6 +120,7 @@ static void completion_check_cache (GCompletion* cmp,
  * Creates a new #GCompletion.
  *
  * Returns: the new #GCompletion.
+ * Deprecated: 2.26: Rarely used API
  **/
 GCompletion* 
 g_completion_new (GCompletionFunc func)