gutils: Remove public API decorator from g_set_user_dirs()

It’s a private API, and is not meant to be exposed in the public API.
Since it’s only used internally within libglib, we don’t have to expose
it in the public symbol table, so drop the decorator.

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

Helps: #2876

glib/gutilsprivate.h

@@ -28,7 +28,6 @@
 
 G_BEGIN_DECLS
 
-GLIB_AVAILABLE_IN_2_60
 void g_set_user_dirs (const gchar *first_dir_type,
                       ...) G_GNUC_NULL_TERMINATED;