Bump actions/attest-build-provenance from 2 to 3 (#13)

Bumps [actions/attest-build-provenance](https://github.com/actions/attest-build-provenance) from 2 to 3.
- [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@v2...v3)

---
updated-dependencies:
- dependency-name: actions/attest-build-provenance
  dependency-version: '3'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/build.yml

@@ -125,7 +125,7 @@ jobs:
 
       - name: Generate artifact attestation
         if: github.ref_type == 'tag'
-        uses: actions/attest-build-provenance@v2
+        uses: actions/attest-build-provenance@v3
         with:
           subject-path: |
             dartsdk-android-${{ matrix.target-arch }}-release.tar.gz