Remove keystoneauth-saml2 from keystone projects list

The keystoneauth-saml2 project is now retired. The repo had no
releases and it's functionality has been rolled into the new
keystoneauth repo.

For more patches related to retiring keystoneauth-saml2, see:
https://review.openstack.org/#/q/branch:master+topic:retire-ksa-saml2

Change-Id: I91975571b5ebc9b1424b3abd5a6e0e183948eb9d

reference/projects.yaml

@@ -1708,12 +1708,6 @@ keystone:
         - release:cycle-with-intermediary
         - type:library
         - release:managed
-    keystoneauth-saml2:
-      repos:
-        - openstack/keystoneauth-saml2
-      tags:
-        - release:independent
-        - type:library
     keystonemiddleware:
       repos:
         - openstack/keystonemiddleware