[gtksourceview] Update link in the HACKING file

[Sébastien Wilmet <swilmet src gnome org>]

commit c93039c12df2c3f7391c8eaf41540c8528a1f9e1
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Sat Aug 22 13:38:25 2015 +0200

    Update link in the HACKING file

 HACKING |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/HACKING b/HACKING
index 9c08036..23b3f44 100644
--- a/HACKING
+++ b/HACKING
@@ -161,8 +161,8 @@ See also
 ========
 
 https://wiki.gnome.org/Apps/Gedit/DevGettingStarted
+https://developer.gnome.org/programming-guidelines/stable/
 https://wiki.gnome.org/Projects/GTK%2B/BestPractices
-ftp://ftp.gnome.org/pub/GNOME/teams/docs/devel/guides/programming_guidelines/
 http://ometer.com/hacking.html
 http://blogs.gnome.org/swilmet/2012/08/01/about-code-quality-and-maintainability/