[gnome-boxes] README: Update bug reporting address

[Felipe Borges <felipeborges src gnome org>]

commit 0076ab7fc806ec3971ff0f6f105bcddb0076320c
Author: Felipe Borges <felipeborges gnome org>
Date:   Fri Feb 9 12:59:16 2018 +0100

    README: Update bug reporting address
    
    We are now on gitlab.gnome.org

 README | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/README b/README
index 8779ee62..b2f65d1f 100644
--- a/README
+++ b/README
@@ -43,7 +43,7 @@ Reporting Bugs
 
 If you want to report bugs, please check if there isn't already one on:
 
- https://bugzilla.gnome.org/buglist.cgi?quicksearch=product%3A%22gnome-boxes%22
+ https://gitlab.gnome.org/GNOME/gnome-boxes/issues
 
 If one does not exist already, please file a new one.