Bump sigstore/cosign-installer from 3.8.2 to 3.9.1

Bumps [sigstore/cosign-installer](https://github.com/sigstore/cosign-installer) from 3.8.2 to 3.9.1.
- [Release notes](https://github.com/sigstore/cosign-installer/releases)
- [Commits](sigstore/cosign-installer@3454372...398d4b0)

---
updated-dependencies:
- dependency-name: sigstore/cosign-installer
  dependency-version: 3.9.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

.github/workflows/build-multiarch.yml

@@ -49,7 +49,7 @@ jobs:
     steps:
       - name: Install cosign
         if: ${{ inputs.sign == true && github.event.release && github.event.action == 'published' }}
-        uses: sigstore/cosign-installer@3454372f43399081ed03b604cb2d021dabca52bb #v3.8.2
+        uses: sigstore/cosign-installer@398d4b0eeef1380460a10c8013a76f728fb906ac #v3.9.1
         with:
           cosign-release: 'v2.2.4'