[gnome-system-monitor] Use libhandy main instead of libhandy master

[Robert Roth <robertroth src gnome org>]

commit 9d372cd47b262a59df9c4ce067e0f15af1ad4986
Author: Robert Roth <robert roth off gmail com>
Date:   Mon Feb 7 11:37:30 2022 +0200

    Use libhandy main instead of libhandy master

 subprojects/libhandy.wrap | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/subprojects/libhandy.wrap b/subprojects/libhandy.wrap
index a3806c8d..100acb97 100644
--- a/subprojects/libhandy.wrap
+++ b/subprojects/libhandy.wrap
@@ -1,4 +1,4 @@
 [wrap-git]
 directory=libhandy
 url=https://gitlab.gnome.org/GNOME/libhandy.git
-revision=origin/master
+revision=origin/main