Bump sigstore/cosign-installer from 3.7.0 to 3.8.0

Bumps [sigstore/cosign-installer](https://github.com/sigstore/cosign-installer) from 3.7.0 to 3.8.0.
- [Release notes](https://github.com/sigstore/cosign-installer/releases)
- [Commits](sigstore/cosign-installer@v3.7.0...v3.8.0)

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

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

Author: dependabot[bot]

.github/workflows/build-image.yml

@@ -58,7 +58,7 @@ jobs:
         uses: docker/setup-buildx-action@v3.8.0
       -
         name: Install Cosign
-        uses: sigstore/cosign-installer@v3.7.0
+        uses: sigstore/cosign-installer@v3.8.0
       -
         name: Login to GitHub Container Registry
         uses: docker/login-action@v3.3.0

.github/workflows/build-split-image.yml

@@ -160,7 +160,7 @@ jobs:
           password: ${{ secrets.GITHUB_TOKEN }}
       -
         name: Install Cosign
-        uses: sigstore/cosign-installer@v3.7.0
+        uses: sigstore/cosign-installer@v3.8.0
       -
         name: Create image tags
         id: image_tags