chore(github): bump actions/cache from 4 to 6

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](actions/cache@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>

Author: dependabot[bot]

.github/workflows/rust_quality.yml

@@ -71,7 +71,7 @@ jobs:
 
       - name: Cache Cargo registry and build artifacts
         id: cache
-        uses: actions/cache@v4
+        uses: actions/cache@v6
         with:
           path: |
             ~/.cargo/registry/index
@@ -133,7 +133,7 @@ jobs:
       # Restore-only: rust_quality(ubuntu) owns the cache write. Saving
       # from here too would race with that job.
       - name: Restore Cargo cache (read-only)
-        uses: actions/cache/restore@v4
+        uses: actions/cache/restore@v6
         with:
           path: |
             ~/.cargo/registry/index