Remove apostrophe (#7868)

## Problem

## Summary of changes

## Checklist before requesting a review

- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.

## Checklist before merging

- [ ] Do not forget to reformat commit message to not include the above
checklist

vm-image-spec.yaml

@@ -320,7 +320,7 @@ files:
 
       - metric_name: wal_is_lost
         type: gauge
-        help: 'Whether or not the replication slot\'s wal_status is lost'
+        help: 'Whether or not the replication slot wal_status is lost'
         key_labels:
           - slot_name
         values: [wal_status_is_lost]