[pitivi] docs: Remove GitHub links

[Thibault Saunier <tsaunier src gnome org>]

commit 90deee29ae7bc1bd75bbf85e5153fe67bd8cc4cb
Author: Alexandru Băluț <alexandru balut gmail com>
Date:   Sat Apr 14 07:38:56 2018 +0200

    docs: Remove GitHub links

 docs/Google_Summer_of_Code.md               | 2 +-
 docs/Testing.md                             | 3 +--
 docs/attic/Setup_development_environment.md | 7 -------
 3 files changed, 2 insertions(+), 10 deletions(-)
---
diff --git a/docs/Google_Summer_of_Code.md b/docs/Google_Summer_of_Code.md
index d7508a22..ebad5384 100644
--- a/docs/Google_Summer_of_Code.md
+++ b/docs/Google_Summer_of_Code.md
@@ -123,7 +123,7 @@ Therefore, you should proceed like this:
   [our official stance]: 
http://jeff.ecchi.ca/blog/2014/02/15/applying-for-a-gsoc-project-is-all-about-early-involvement-and-commitment/
   [Being selected as a Summer of Code student]: http://ploum.net/be-selected-student-for-soc/
   [IRC channel]: http://www.pitivi.org/?go=contact
-  [development environment]: https://github.com/pitivi/pitivi/blob/master/docs/HACKING.md
+  [development environment]: HACKING.md
   [Test suite]: Testing.md
   [issue]: https://gitlab.gnome.org/GNOME/pitivi/issues
   [fun tasks for newcomers]: https://gitlab.gnome.org/GNOME/pitivi/issues?label_name%5B%5D=4.+Newcomers
diff --git a/docs/Testing.md b/docs/Testing.md
index f1b3a528..d40b8f48 100644
--- a/docs/Testing.md
+++ b/docs/Testing.md
@@ -39,8 +39,7 @@ as of [0.94](releases/0.94.md).
 
 If you're curious about our unit tests, the best way to get to know them
 is to write a few Pitivi unit tests and have us review them. Check out
-[how to set up your dev
-env](https://github.com/pitivi/pitivi/blob/master/docs/HACKING.md) and
+[how to set up your dev env](HACKING.md) and
 come in our [IRC channel](http://www.pitivi.org/?go=contact)!
 
 ## Integration tests