build(deps): bump sigstore/cosign-installer

Bumps [sigstore/cosign-installer](https://github.com/sigstore/cosign-installer) from ef0e9691595ea19ec990a46b1a591dcafe568f34 to a5d81fb6bdbcbb3d239e864d6552820420254494.
- [Release notes](https://github.com/sigstore/cosign-installer/releases)
- [Commits](sigstore/cosign-installer@ef0e969...a5d81fb)

---
updated-dependencies:
- dependency-name: sigstore/cosign-installer
  dependency-type: direct:production
...

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

.github/workflows/goreleaser.yml

@@ -25,7 +25,7 @@ jobs:
       with:
         go-version: "1.18"
         check-latest: true
-    - uses: sigstore/cosign-installer@ef0e9691595ea19ec990a46b1a591dcafe568f34 # tag=v2.8.1
+    - uses: sigstore/cosign-installer@a5d81fb6bdbcbb3d239e864d6552820420254494 # tag=v2.8.1
     - name: Set up QEMU
       uses: docker/setup-qemu-action@2b82ce82d56a2a04d2637cd93a637ae1b359c0a7 # tag=v2.2.0
     - name: Docker login