added missing audio_off_user() callback (#15457)

Co-authored-by: Raoul Rubien <raoul.rubienr@gmail.com>

quantum/audio/audio.c

@@ -160,6 +160,8 @@ void audio_toggle(void) {
     eeconfig_update_audio(audio_config.raw);
     if (audio_config.enable) {
         audio_on_user();
+    } else {
+        audio_off_user();
     }
 }
 
@@ -172,6 +174,7 @@ void audio_on(void) {
 
 void audio_off(void) {
     PLAY_SONG(audio_off_song);
+    audio_off_user();
     wait_ms(100);
     audio_stop_all();
     audio_config.enable = 0;

quantum/process_keycode/process_audio.c

@@ -57,3 +57,4 @@ void process_audio_noteoff(uint8_t note) { stop_note(compute_freq_for_midi_note(
 void process_audio_all_notes_off(void) { stop_all_notes(); }
 
 __attribute__((weak)) void audio_on_user() {}
+__attribute__((weak)) void audio_off_user() {}

quantum/process_keycode/process_audio.h

@@ -8,3 +8,4 @@ void process_audio_noteoff(uint8_t note);
 void process_audio_all_notes_off(void);
 
 void audio_on_user(void);
+void audio_off_user(void);