Redirect security-analysis docs to readme

The security-analysis repository has been retired.

https://lists.openstack.org/pipermail/openstack-discuss/2022-June/028816.html

Depends-On: https://review.opendev.org/844463
Change-Id: I7772c73ad1f119218d417ab8df14c81ee8d822ee

tools/www-generator.py

@@ -501,6 +501,7 @@ _RETIRED_REPOS = [
     'openstack/searchlight',
     'openstack/searchlight-specs',
     'openstack/searchlight-ui',
+    'openstack/security-analysis',
     'openstack/sushy-cli',
     'openstack/syntribos',
     'openstack/tempest-horizon',