[devhelp] HACKING file: set text width to 80 chars

[Sébastien Wilmet <swilmet src gnome org>]

commit dc7633b1c9ad732e2c79a1172c7b8aa7d7f31291
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Thu May 24 16:42:13 2018 +0200

    HACKING file: set text width to 80 chars
    
    I copied that sentence from GtkSourceView and forgot to re-wrap the
    text.

 HACKING | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/HACKING b/HACKING
index ad28c86f..cd995ea8 100644
--- a/HACKING
+++ b/HACKING
@@ -1,8 +1,8 @@
 How to contribute to Devhelp
 ============================
 
-Devhelp is hosted on the GNOME GitLab instance, you can fork the
-repository and then do a merge request:
+Devhelp is hosted on the GNOME GitLab instance, you can fork the repository and
+then do a merge request:
 
     https://gitlab.gnome.org/GNOME/devhelp