chore(deps): bump actions/cache from 4 to 6 (#10704)

Bumps [actions/cache](https://github.com/actions/cache) from 4 to 6.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](https://github.com/actions/cache/compare/v4...v6)

---
updated-dependencies:
- dependency-name: actions/cache
  dependency-version: '6'
  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>

.github/workflows/realtime-conformance.yml

@@ -54,7 +54,7 @@ jobs:
           go-version: ${{ matrix.go-version }}
           cache: false
       - name: Cache FizzBee
-        uses: actions/cache@v4
+        uses: actions/cache@v6
         with:
           path: .tools/fizzbee
           key: fizzbee-v0.5.2-${{ runner.os }}-${{ hashFiles('formal-verification/fizzbee.sha256') }}