build(deps): bump pnpm/action-setup from 5 to 6 (#7502)

Bumps [pnpm/action-setup](https://github.com/pnpm/action-setup) from 5 to 6.
- [Release notes](https://github.com/pnpm/action-setup/releases)
- [Commits](https://github.com/pnpm/action-setup/compare/v5...v6)

---
updated-dependencies:
- dependency-name: pnpm/action-setup
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/update-plugins.yml

@@ -12,7 +12,7 @@ jobs:
       - name: Check out etherpad-lite
         uses: actions/checkout@v6
 
-      - uses: pnpm/action-setup@v5
+      - uses: pnpm/action-setup@v6
         name: Install pnpm
         with:
           version: 10