Bump sigstore/cosign-installer from 2.8.0 to 2.8.1

Bumps [sigstore/cosign-installer](https://github.com/sigstore/cosign-installer) from 2.8.0 to 2.8.1.
- [Release notes](https://github.com/sigstore/cosign-installer/releases)
- [Commits](7cc35d7fdb...9becc61764)

---
updated-dependencies:
- dependency-name: sigstore/cosign-installer
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/docker-publish.yml

@@ -41,7 +41,7 @@ jobs:
       # https://github.com/sigstore/cosign-installer
       - name: Install cosign
         if: github.event_name != 'pull_request'
-        uses: sigstore/cosign-installer@7cc35d7fdbe70d4278a0c96779081e6fac665f88 #v2.6.0
+        uses: sigstore/cosign-installer@9becc617647dfa20ae7b1151972e9b3a2c338a2b #v2.6.0
         with:
           cosign-release: 'v1.11.0'