chore(deps): bump sigstore/cosign-installer from 3.7.0 to 3.8.1

Bumps [sigstore/cosign-installer](https://github.com/sigstore/cosign-installer) from 3.7.0 to 3.8.1.
- [Release notes](https://github.com/sigstore/cosign-installer/releases)
- [Commits](sigstore/cosign-installer@v3.7.0...v3.8.1)

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

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

Author: dependabot[bot]

.github/workflows/build-verify.yml

@@ -52,7 +52,7 @@ jobs:
           fi
 
       - name: Install Cosign
-        uses: sigstore/cosign-installer@v3.7.0
+        uses: sigstore/cosign-installer@v3.8.1
 
       - name: Set up QEMU
         if: github.repository_owner == 'microcks' && env.PACKAGE_IMAGE == 'true'