[gedit/gnome-3-8-backport] Use absolute path for libgd submodule

[Jeremy Bicha <jbicha src gnome org>]

commit e2da42744c1410262f8a5a7b0e2121782dafdd65
Author: Ken VanDine <ken vandine canonical com>
Date:   Wed Feb 6 15:05:42 2019 -0500

    Use absolute path for libgd submodule
    
    This is needed to fix Launchpad's git import

 .gitmodules | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/.gitmodules b/.gitmodules
index 303eb9bcb..66989de51 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,3 +1,3 @@
 [submodule "libgd"]
        path = libgd
-       url = ../libgd
+       url = https://gitlab.gnome.org/GNOME/libgd.git