[pitivi] docs: Fix link to proxy editing requirements

[Thibault Saunier <tsaunier src gnome org>]

commit 00ca27af560ccce3befdac5406ab7c23580df557
Author: Alexandru Băluț <alexandru balut gmail com>
Date:   Sat Apr 14 23:36:24 2018 +0200

    docs: Fix link to proxy editing requirements

 docs/Past_GSoCs.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/docs/Past_GSoCs.md b/docs/Past_GSoCs.md
index e0430cb6..52207d1b 100644
--- a/docs/Past_GSoCs.md
+++ b/docs/Past_GSoCs.md
@@ -42,7 +42,7 @@ get involved.
 
 -   Anton Belka worked on the initial
     implementation of proxies in [GES](GES.md) (see [proxy
-    editing requirements](proxy_editing_requirements.md)).
+    editing requirements](design/proxy_editing_requirements.md)).
 -   Mathieu Duponchelle worked on heavy
     bugfixing all across the Pitivi, [GES](GES.md) and GStreamer
     stack, allowing us to release [0.91](releases/0.91.md) at the end of