[glade] CONTRIBUTING.md: update coding style link

[Juan Pablo Ugarte <jpu src gnome org>]

commit 8e38e9a5c8ba80df0c0b1b96fff8fa9ce63582b9
Author: Juan Pablo Ugarte <juanpablougarte gmail com>
Date:   Fri Sep 25 19:16:12 2020 -0300

    CONTRIBUTING.md: update coding style link

 CONTRIBUTING.md | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 67d99cd1..1f716f57 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -34,9 +34,9 @@ git format-patch HEAD^
 
 Coding Style
 ~~~~~~~~~~~~
-Code in Glade should follow the GNOME Programming Guidelines
-(http://developer.gnome.org/doc/guides/programming-guidelines/),
-basically this means being consistent with the sorrounding code.
+Code in Glade should follow the GNU style of GNOME Programming Guidelines
+(https://developer.gnome.org/programming-guidelines/stable/c-coding-style.html.en),
+basically this means being consistent with the surrounding code.
 The only exception is that we prefer having braces always on a new line
 e.g.: