build(deps): Bump dawidd6/action-download-artifact in /.github/workflows

Bumps [dawidd6/action-download-artifact](https://github.com/dawidd6/action-download-artifact) from 2.11.0 to 6.
- [Release notes](https://github.com/dawidd6/action-download-artifact/releases)
- [Commits](dawidd6/action-download-artifact@v2.11.0...v6)

---
updated-dependencies:
- dependency-name: dawidd6/action-download-artifact
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/dependabot-merge.yml

@@ -14,7 +14,7 @@ jobs:
       group: ukcp-api-dependabot-auto-merge
     steps:
       - name: Download Pull Request Number
-        uses: dawidd6/action-download-artifact@v2.11.0
+        uses: dawidd6/action-download-artifact@v6
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
           workflow: test.yml