[gnome-control-center] sound: Remove unused files

[Robert Ancell <rancell src gnome org>]

commit 7a65d113f29f85002e03761427e432739b857b07
Author: Robert Ancell <robert ancell canonical com>
Date:   Thu Mar 19 16:22:20 2020 +1300

    sound: Remove unused files
    
    These were accidentally added as part of ths sound panel redesign.

 panels/sound/cc-alert-selector.h  | 28 ----------------------------
 panels/sound/cc-alert-selector.ui | 31 -------------------------------
 po/POTFILES.in                    |  1 -
 3 files changed, 60 deletions(-)
---
diff --git a/po/POTFILES.in b/po/POTFILES.in
index 4c7c4781a..e58a1bef5 100644
--- a/po/POTFILES.in
+++ b/po/POTFILES.in
@@ -196,7 +196,6 @@ panels/sharing/gnome-sharing-panel.desktop.in.in
 panels/sharing/org.gnome.controlcenter.remote-login-helper.policy.in.in
 panels/sound/cc-alert-chooser.c
 panels/sound/cc-alert-chooser.ui
-panels/sound/cc-alert-selector.ui
 panels/sound/cc-balance-slider.ui
 panels/sound/cc-fade-slider.ui
 panels/sound/cc-output-test-dialog.c