[libglnx] README: Update Contributing

[Colin Walters <walters src gnome org>]

commit 1e9b30838ea1101d7e3e924ddc58057842b8f3bf
Author: Colin Walters <walters verbum org>
Date:   Fri Nov 30 16:27:19 2018 -0500

    README: Update Contributing

 README.md | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)
---
diff --git a/README.md b/README.md
index f2ae6ae..6589d29 100644
--- a/README.md
+++ b/README.md
@@ -44,9 +44,7 @@ APIs not defined in GLib yet, such as `glnx_autofd`.
 Contributing
 ------------
 
-Currently there is not a Bugzilla product - one may be created
-in the future.  You can submit PRs against the Github mirror:
+Development happens in GNOME Gitlab: https://gitlab.gnome.org/GNOME/libglnx
 
-https://github.com/GNOME/libglnx/pulls
-
-Or alternatively, email one of the maintainers directly.
+(If you're seeing this on the Github mirror, we used to do development
+ on Github but that was before GNOME deployed Gitlab.)