[gnome-flashback] sound-applet: update submodule

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 4f56e7c3f865594c65c80d1e5f439644335b955a
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Mon Sep 10 13:54:00 2018 +0300

    sound-applet: update submodule

 gnome-flashback/libsound-applet/gvc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/gnome-flashback/libsound-applet/gvc b/gnome-flashback/libsound-applet/gvc
index ce8e488..7de39e7 160000
--- a/gnome-flashback/libsound-applet/gvc
+++ b/gnome-flashback/libsound-applet/gvc
@@ -1 +1 @@
-Subproject commit ce8e4880ce31e275c40825c4ed756c791107f810
+Subproject commit 7de39e768e769a075e1057b7d6a1b948fcce274a