elastic: Use specific image loader version

Related to T4144

sysadmin/T3592-elastic-workers/worker/values.yaml

@@ -13,7 +13,7 @@ storage:
 swh:
   loader:
     image: softwareheritage/loaders
-    version: latest
+    version: 2022-04-28
     replicas:
       min: 1
       max: 10

[Phabricator Migration user]

Some references in the commit message have been migrated:

• T4144 is now swh/infra/sysadm-environment#4144 (closed)