Fix link to security bug reporting process (#2160)

The wiki changed and the link is now dangling. This change
fixes the link.

Signed-off-by: Arnaud J Le Hors <lehors@us.ibm.com>
(cherry picked from commit 9890b37)

docs/source/CONTRIBUTING.rst

@@ -231,7 +231,7 @@ reported, then you might add a comment that you also are interested in seeing
 the defect fixed.
 
 .. note:: If the defect is security-related, please follow the Hyperledger
-          `security bug reporting process <https://wiki.hyperledger.org/display/HYP/Defect+Response>`__.
+          `security bug reporting process <https://wiki.hyperledger.org/display/SEC/Defect+Response>`__.
 
 If it has not been previously reported, you may either submit a PR with a
 well documented commit message describing the defect and the fix, or you