[gnome-control-center] sound: Update gvc to latest version

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit e98d0eef05782e82efde9c5ac76099ea64daac49
Author: Robert Ancell <robert ancell canonical com>
Date:   Thu Feb 7 10:06:57 2019 +1300

    sound: Update gvc to latest version
    
    This fixes compile warnings

 subprojects/gvc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/subprojects/gvc b/subprojects/gvc
index 67533bffd..ae1a34aaf 160000
--- a/subprojects/gvc
+++ b/subprojects/gvc
@@ -1 +1 @@
-Subproject commit 67533bffdcd22893b28baa411b2e75bd75dce323
+Subproject commit ae1a34aafce7026b8c0f65a43c9192d756fe1057