[Tempest Plugins] Tag stein-last

Stein branch is in Extended Maintenance now[1]. All Tempest
plugins are branchless which means master version of Tempest
and its plugins is used to test the supported stable branches.

Once stable branch is moved to EM state then, Tempest and its
plugins compatible tag needs to be released so that we can
keep testing the EM stable branches with this tag once master
Tempest and its plugins are not compatible[2].

This tag will help for testing the stable/stein with single
compatible tag of Tempest and its plugins.

Tagging 'stein-last' as well as a new version also with same hash.
Documenting this new tag name here
- https://review.opendev.org/c/openstack/project-team-guide/+/769821

More detail on compatible version policy for Tempest and its
plugins is here
- https://docs.openstack.org/tempest/latest/tempest_and_plugins_compatible_version_policy.html

[1] https://releases.openstack.org/stein/index.html
[2] https://docs.openstack.org/tempest/latest/stable_branch_support_policy.html

Change-Id: If117a9da3094e012a308a4a559fcb56a4b815bec

deliverables/stein/keystone-tempest-plugin.yaml

@@ -13,3 +13,8 @@ releases:
       - repo: openstack/keystone-tempest-plugin
         hash: b573efb357ad1abba0227357015aa0d782e40541
         tarball-base: keystone_tempest_plugin
+  - version: stein-last
+    projects:
+      - repo: openstack/keystone-tempest-plugin
+        hash: 774bb4f905f1626bb30802f5c21205761ccc88d2
+        tarball-base: keystone_tempest_plugin

deliverables/wallaby/keystone-tempest-plugin.yaml

@@ -9,3 +9,8 @@ repository-settings:
     tarball-base: keystone_tempest_plugin
 team: keystone
 type: tempest-plugin
+releases:
+  - version: 0.6.0
+    projects:
+      - repo: openstack/keystone-tempest-plugin
+        hash: 774bb4f905f1626bb30802f5c21205761ccc88d2