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](3454372f43...398d4b0eee)

---
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>

.github/workflows/release.yaml

@@ -17,7 +17,7 @@ jobs:
       - name: Clone repo
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 #v4.2.2
       - name: Setup Cosign
-        uses: sigstore/cosign-installer@3454372f43399081ed03b604cb2d021dabca52bb #v3.8.2
+        uses: sigstore/cosign-installer@398d4b0eeef1380460a10c8013a76f728fb906ac #v3.9.1
       - name: Setup Helm
         uses: azure/setup-helm@b9e51907a09c216f16ebe8536097933489208112 #v4.3.0
         with: