Also allow deletions as valid changelog changes

Else this workflow fails for release PRs that only remove files from
`.changie/unreleased`

.github/workflows/check-changelog.yml

@@ -27,7 +27,7 @@ jobs:
  with:
  filters: |
  exists:
- - added|modified: '.changes/unreleased/**.yaml'
+ - '.changes/unreleased/**.yaml'
 
  - name: Fail job if changelog entry is missing and required
  if: steps.changelog_check.outputs.exists == 'false'