[libpanel] Update POTFILES.in

[Piotr Drąg <piotrdrag src gnome org>]

commit 6fa614d194f96e02e1cf5519ff2a6142e16ee78c
Author: Piotr Drąg <piotrdrag gmail com>
Date:   Sun Sep 11 12:54:28 2022 +0200

    Update POTFILES.in

 po/POTFILES.in | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/po/POTFILES.in b/po/POTFILES.in
index a013c11..fab3787 100644
--- a/po/POTFILES.in
+++ b/po/POTFILES.in
@@ -1,7 +1,7 @@
-src/panel-frame-header-bar.c
+# List of source files containing translatable strings.
+# Please keep this file sorted alphabetically.
 src/panel-frame-header-bar.ui
 src/panel-frame.ui
 src/panel-maximized-controls.c
-src/panel-save-dialog.c
 src/panel-save-dialog.ui
-src/panel-signal-group.c
+src/panel-theme-selector.ui