docs: remove broken link

Author: radeva

CONTRIBUTING.md

@@ -59,7 +59,7 @@ git checkout -b <my-fix-branch> master
 
 4. Before you submit your PR:
     - Rebase your changes to the latest master: `git pull --rebase upstream master`.
-    - Ensure all unit test are green. Check [running unit tests](DevelopmentWorkflow.md#running-the-tests). How?
+    - Ensure all unit test are green. How?
          - Go to `seed-tests`
          - Delete `seed-copy` if existing
          - Run `npm install`