[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: I011f9be8ae7fbf9fbd638ec769e0fad53531563d

deliverables/stein/octavia-tempest-plugin.yaml

@@ -12,3 +12,7 @@ releases:
       - hash: c9414e8419322815dc97a1919f19a44a0044c151
         repo: openstack/octavia-tempest-plugin
     version: 1.0.0
+  - version: stein-last
+    projects:
+      - repo: openstack/octavia-tempest-plugin
+        hash: efae4470eb91859b6957d9280f0c60de25da54e8

deliverables/wallaby/octavia-tempest-plugin.yaml

@@ -8,3 +8,8 @@ repository-settings:
 storyboard: 908
 team: octavia
 type: tempest-plugin
+releases:
+  - version: 1.6.0
+    projects:
+      - repo: openstack/octavia-tempest-plugin
+        hash: efae4470eb91859b6957d9280f0c60de25da54e8