[libglnx/readme-libgsystem] README: update link to libgsystem

[Will Thompson <wjt src gnome org>]

commit 70988f02872d5bb3a4123e6b98106acd2150f400
Author: Will Thompson <will willthompson co uk>
Date:   Fri Nov 29 21:05:14 2019 +0000

    README: update link to libgsystem
    
    I was curious.

 README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/README.md b/README.md
index 3be38d7..587e5d4 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-libglnx is the successor to libgsystem: https://git.gnome.org/browse/libgsystem
+libglnx is the successor to [libgsystem](https://gitlab.gnome.org/Archive/libgsystem).
 
 It is for modules which depend on both GLib and Linux, intended to be
 used as a git submodule.