Bump actions/attest-build-provenance from 2.0.1 to 2.1.0 (#2952)

Bumps [actions/attest-build-provenance](https://github.com/actions/attest-build-provenance) from 2.0.1 to 2.1.0.
- [Release notes](https://github.com/actions/attest-build-provenance/releases)
- [Changelog](https://github.com/actions/attest-build-provenance/blob/main/RELEASE.md)
- [Commits](actions/attest-build-provenance@c4fbc64...7668571)

---
updated-dependencies:
- dependency-name: actions/attest-build-provenance
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

.github/workflows/build.yml

@@ -128,7 +128,7 @@ jobs:
         dotnet publish ./src/LondonTravel.Site --arch x64 --os linux -p:PublishProfile=DefaultContainer
 
     - name: Attest container image
-      uses: actions/attest-build-provenance@c4fbc648846ca6f503a13a2281a5e7b98aa57202 # v2.0.1
+      uses: actions/attest-build-provenance@7668571508540a607bdfd90a87a560489fe372eb # v2.1.0
       if: steps.publish-container.outputs.container-digest != ''
       with:
         push-to-registry: true