Bump actions/cache from 5 to 6 (#5824)

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](https://github.com/actions/cache/compare/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>

.github/workflows/build.yml

@@ -40,7 +40,7 @@ jobs:
 
     - name: Restore cached libhevtun
       id: cache-libhevtun-restore
-      uses: actions/cache/restore@v5
+      uses: actions/cache/restore@v6
       with:
         path: ${{ github.workspace }}/libs
         key: libhevtun-${{ runner.os }}-${{ env.NDK_HOME }}-${{ hashFiles('.git/modules/hev-socks5-tunnel/HEAD') }}-${{ hashFiles('compile-hevtun.sh') }}
@@ -52,7 +52,7 @@ jobs:
     
     - name: Save libhevtun
       if: steps.cache-libhevtun-restore.outputs.cache-hit != 'true'
-      uses: actions/cache/save@v5
+      uses: actions/cache/save@v6
       with:
         path: ${{ github.workspace }}/libs
         key: libhevtun-${{ runner.os }}-${{ env.NDK_HOME }}-${{ hashFiles('.git/modules/hev-socks5-tunnel/HEAD') }}-${{ hashFiles('compile-hevtun.sh') }}