[gnome-control-center] Bump libhandy to a commit fixing its static installation

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

commit 6a2b991577ec2b7a6273e37a387d5ac575650d92
Author: Adrien Plazas <kekun plazas laposte net>
Date:   Tue Jan 29 14:09:03 2019 +0100

    Bump libhandy to a commit fixing its static installation
    
    The other commits shouldn't affect the application in any way, so it's
    safe to bump, especially as it's needed only by the submodule.
    
    Fixes https://gitlab.gnome.org/GNOME/gnome-control-center/issues/350.

 subprojects/libhandy | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/subprojects/libhandy b/subprojects/libhandy
index fac9fa59a..607152c2d 160000
--- a/subprojects/libhandy
+++ b/subprojects/libhandy
@@ -1 +1 @@
-Subproject commit fac9fa59a83f47655d604796632a932d58cf60bb
+Subproject commit 607152c2d1abd3270ba8896dbb823bc2b7534c19