[storlets] Transition EM branches to Unmaintained

With the new TC resolution the community replaces Extended Maintenance
with Unmaintained status [1].

So this patch transitions victoria, wallaby, and xena EM branches to
Unmaintained as follows:
- tip of the given branch will be tagged with <series>-eom tag
- unmaintained/<series> branch will be cut from <series>-eom tag
- stable/<series> branch will be deleted

Some further notes:
- stable policy still applies
- backports can be pushed against unmaintained/<series> branch
- openstack-unmaintained-core group have the rights to merge patches

For further details please read the resolution [1] & review and +1 this
patch if this is correct as soon as possible.

[1] https://governance.openstack.org/tc/resolutions/20230724-unmaintained-branches.html

Change-Id: I95850700c8ea52038580df7c8318d1b39e464940

deliverables/wallaby/storlets.yaml

@@ -19,7 +19,13 @@ releases:
     projects:
       - repo: openstack/storlets
         hash: f8e8ecb2b8c49f446beaf42805619c3d0523d070
+  - version: wallaby-eom
+    projects:
+      - repo: openstack/storlets
+        hash: d6edad01309e06baadd84fa7af9fa5d7e0fc05e2
 branches:
   - name: stable/wallaby
     location: 7.0.0.0rc1
+  - name: unmaintained/wallaby
+    location: wallaby-eom
 release-notes: https://docs.openstack.org/releasenotes/storlets/wallaby.html

deliverables/xena/storlets.yaml

@@ -19,7 +19,13 @@ releases:
     projects:
       - repo: openstack/storlets
         hash: a513114c33d414037ec80bc6c5722dae52a90410
+  - version: xena-eom
+    projects:
+      - repo: openstack/storlets
+        hash: b524ed936708d74bb9c5064da6866879feb67a14
 branches:
   - name: stable/xena
     location: 8.0.0.0rc1
+  - name: unmaintained/xena
+    location: xena-eom
 release-notes: https://docs.openstack.org/releasenotes/storlets/xena.html