Fix links to the exercise directories

After building the documentation all links are now working properly in
the browser, without any further steps.

Change-Id: I6ba8f619b798753afc133fc9c492681923e021b3

presentations/git-gerrit-workshop/index.txt

diff --git a/presentations/git-gerrit-workshop/index.txt b/presentations/git-gerrit-workshop/index.txt
index 313a364..e40582f 100644
--- a/presentations/git-gerrit-workshop/index.txt
+++ b/presentations/git-gerrit-workshop/index.txt
@@ -2,5 +2,5 @@
 
 * link:abstract.html[Training Abstract]
 * link:git-gerrit-workshop.html[Slides]
-* link:../../exercises/egit/git/index.html[Git Exercises]
-* link:../../exercises/gerrit/egit/index.html[Gerrit Exercises]
+* link:../../target/exercises/egit/git/index.html[Git Exercises]
+* link:../../target/exercises/egit/gerrit/index.html[Gerrit Exercises]