chore(deps): update sigstore/sigstore-conformance action to v0.0.18

Author: renovate[bot]

.github/workflows/conformance.yml

@@ -43,7 +43,7 @@ jobs:
           java-version: ${{ matrix.java-version }}
           distribution: 'temurin'
 
-      - uses: sigstore/sigstore-conformance@640e7dfb715518eeeb492910c6d244cedcc6cfea # v0.0.17
+      - uses: sigstore/sigstore-conformance@fd90e6b0f3046f2276a6659481de6df495dea3b9 # v0.0.18
         with:
           entrypoint: ${{ github.workspace }}/bin/sigstore-cli
           environment: ${{ matrix.sigstore-env }}