ci: bump actions/attest-build-provenance from 3 to 4

Bumps [actions/attest-build-provenance](https://github.com/actions/attest-build-provenance) from 3 to 4.
- [Release notes](https://github.com/actions/attest-build-provenance/releases)
- [Changelog](https://github.com/actions/attest-build-provenance/blob/main/RELEASE.md)
- [Commits](https://github.com/actions/attest-build-provenance/compare/v3...v4)

---
updated-dependencies:
- dependency-name: actions/attest-build-provenance
  dependency-version: '4'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/appimage-build.yml

@@ -308,7 +308,7 @@ jobs:
 
       - name: Attest AppImage (Build Provenance)
         if: ${{ github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name == github.repository }}
-        uses: actions/attest-build-provenance@v3
+        uses: actions/attest-build-provenance@v4
         with:
           subject-path: Zoitechat-*-x86_64.AppImage