Bump sigstore/sigstore-conformance from 0.0.12 to 0.0.13 (#345)

Bumps [sigstore/sigstore-conformance](https://github.com/sigstore/sigstore-conformance) from 0.0.12 to 0.0.13.
- [Release notes](https://github.com/sigstore/sigstore-conformance/releases)
- [Commits](sigstore/sigstore-conformance@e472219...6bd1c54)

---
updated-dependencies:
- dependency-name: sigstore/sigstore-conformance
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/conformance.yml

@@ -42,11 +42,11 @@ jobs:
 
       - run: go build -o conformance cmd/conformance/main.go
 
-      - uses: sigstore/sigstore-conformance@e472219febb4fe9c6ce62033be8a811963ef4f27 # v0.0.12
+      - uses: sigstore/sigstore-conformance@6bd1c54e236c9517da56f7344ad16cc00439fe19 # v0.0.13
         with:
           entrypoint: ${{ github.workspace }}/conformance
 
-      - uses: sigstore/sigstore-conformance@e472219febb4fe9c6ce62033be8a811963ef4f27 # v0.0.12
+      - uses: sigstore/sigstore-conformance@6bd1c54e236c9517da56f7344ad16cc00439fe19 # v0.0.13
         with:
           entrypoint: ${{ github.workspace }}/conformance
           environment: staging