Bump slsa-framework/slsa-github-generator from 1.5.0 to 2.1.0

Bumps [slsa-framework/slsa-github-generator](https://github.com/slsa-framework/slsa-github-generator) from 1.5.0 to 2.1.0.
- [Release notes](https://github.com/slsa-framework/slsa-github-generator/releases)
- [Changelog](https://github.com/slsa-framework/slsa-github-generator/blob/main/CHANGELOG.md)
- [Commits](slsa-framework/slsa-github-generator@v1.5.0...v2.1.0)

---
updated-dependencies:
- dependency-name: slsa-framework/slsa-github-generator
  dependency-version: 2.1.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/release.yml

@@ -58,7 +58,7 @@ jobs:
       actions: read
       contents: write
       id-token: write # Needed to access the workflow's OIDC identity.
-    uses: "slsa-framework/slsa-github-generator/.github/workflows/generator_generic_slsa3.yml@v1.5.0"
+    uses: "slsa-framework/slsa-github-generator/.github/workflows/generator_generic_slsa3.yml@v2.1.0"
     with:
       base64-subjects: "${{ needs.build.outputs.hashes }}"
       upload-assets: true