[jhbuild] Update git clone command from git.gnome.org to gitlab.gnome.org

[Andre Klapper <aklapper src gnome org>]

commit 58c70eb996d562ba8ae8a07e699012541edeab85
Author: Andre Klapper <a9016009 gmx de>
Date:   Sun Oct 28 19:35:31 2018 +0100

    Update git clone command from git.gnome.org to gitlab.gnome.org

 doc/C/index.docbook | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/doc/C/index.docbook b/doc/C/index.docbook
index f47eb79b..a1c28876 100644
--- a/doc/C/index.docbook
+++ b/doc/C/index.docbook
@@ -97,7 +97,7 @@
         all source code will be installed, for example,
         <filename>~/jhbuild/checkout</filename>.</para>
 
-<screen><prompt>$</prompt> <userinput>git clone git://git.gnome.org/jhbuild</userinput>
+<screen><prompt>$</prompt> <userinput>git clone https://gitlab.gnome.org/GNOME/jhbuild.git</userinput>
 <computeroutput>...</computeroutput>
 <prompt>$</prompt></screen>