chore(deps): update sigstore/cosign-installer action to v3.9.1

| datasource  | package                   | from   | to     |
| ----------- | ------------------------- | ------ | ------ |
| github-tags | sigstore/cosign-installer | v3.6.0 | v3.9.1 |

Author: stackable-bot

.github/workflows/pr_cockpit.yml

@@ -106,7 +106,7 @@ jobs:
           go-version: ${{ env.GO_VERSION }}
 
       - name: Install cosign
-        uses: sigstore/cosign-installer@4959ce089c160fddf62f7b42464195ba1a56d382 # v3.6.0
+        uses: sigstore/cosign-installer@398d4b0eeef1380460a10c8013a76f728fb906ac # v3.9.1
 
       - name: Install syft
         uses: anchore/sbom-action/download-syft@61119d458adab75f756bc0b9e4bde25725f86a7a # v0.17.2
@@ -149,7 +149,7 @@ jobs:
       OCI_REGISTRY_SDP_CHARTS_USERNAME: "robot$sdp-charts+github-action-build"
     steps:
       - name: Install cosign
-        uses: sigstore/cosign-installer@4959ce089c160fddf62f7b42464195ba1a56d382 # v3.6.0
+        uses: sigstore/cosign-installer@398d4b0eeef1380460a10c8013a76f728fb906ac # v3.9.1
       - name: Checkout
         uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332 # v4.1.7
         with: