Resolve "Geo::RepositoryVerification::Secondary::ShardWorker lease key is not namespaced by shard name"

What does this MR do?

Adds a namespace with the shard name for the lease key in the repository verification job for a secondary node.

With a namespaced lease key, multiple jobs can run at the same time (one for each unique shard).

This fix the previous behavior where only the first job was executing, failing for all the other shards.

What are the relevant issue numbers?

#7722 (closed) gitlab-org/gitlab-ee#6980

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• EE specific content should be in the top level /ee folder

Closes #7722 (closed)