ci: bump actions/cache from 5 to 6 (#152)

Bumps [actions/cache](https://github.com/actions/cache) from 5 to 6.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v5...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>

Author: dependabot[bot]

.github/workflows/fuzz.yml

@@ -75,7 +75,7 @@ jobs:
         run: cargo install cargo-fuzz
 
       - name: Restore corpus
-        uses: actions/cache@v5
+        uses: actions/cache@v6
         with:
           path: fuzz/corpus/${{ matrix.target }}
           key: fuzz-corpus-${{ matrix.target }}-${{ github.sha }}
@@ -105,7 +105,7 @@ jobs:
 
       - name: Save corpus
         if: always()
-        uses: actions/cache/save@v5
+        uses: actions/cache/save@v6
         with:
           path: fuzz/corpus/${{ matrix.target }}
           key: fuzz-corpus-${{ matrix.target }}-${{ github.sha }}
@@ -204,7 +204,7 @@ jobs:
         run: cargo install cargo-fuzz
 
       - name: Restore all corpora
-        uses: actions/cache@v5
+        uses: actions/cache@v6
         with:
           path: fuzz/corpus/
           key: fuzz-corpus-all-${{ github.sha }}