pidgin/pidgin

Fix the docs that were broken when the sound api was removed

Update the docs for the sound api removal

Testing Done:
Built libpurple-doc, finch-doc, pidgin-doc, and facebook-doc, verified no errors.

Reviewed at https://reviews.imfreedom.org/r/68/
#if !defined(PIDGIN_GLOBAL_HEADER_INSIDE) && !defined(PIDGIN_COMPILATION)
# error "only <pidgin.h> may be included directly"
#endif
#ifndef PIDGIN_ABOUT_H
#define PIDGIN_ABOUT_H
/**
* SECTION:pidginabout
* @section_id: pidgin-about
* @short_description: <filename>pidginabout.h</filename>
* @title: About Dialog
*/
#include <gtk/gtk.h>
G_BEGIN_DECLS
#define PIDGIN_TYPE_ABOUT_DIALOG (pidgin_about_dialog_get_type())
G_DECLARE_FINAL_TYPE(PidginAboutDialog, pidgin_about_dialog, PIDGIN,
ABOUT_DIALOG, GtkDialog)
GtkWidget *pidgin_about_dialog_new(void);
G_END_DECLS
#endif /* PIDGIN_ABOUT_H */