Bump actions/cache from 4 to 5 (#6596)

Bumps [actions/cache](https://github.com/actions/cache) from 4 to 5.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v4...v5)

---
updated-dependencies:
- dependency-name: actions/cache
  dependency-version: '5'
  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/pnnx.yml

@@ -94,21 +94,21 @@ jobs:
 
     - name: cache-libtorch
       id: cache-libtorch
-      uses: actions/cache@v4
+      uses: actions/cache@v5
       with:
         path: libtorch-${{ env.LIBTORCH_VERSION }}-install
         key: libtorch-${{ env.LIBTORCH_VERSION }}-linux-install-${{ env.CACHE_DATE }}
 
     - name: cache-torchvision
       id: cache-torchvision
-      uses: actions/cache@v4
+      uses: actions/cache@v5
       with:
         path: torchvision-${{ env.TORCHVISION_VERSION }}-install
         key: torchvision-${{ env.TORCHVISION_VERSION }}-linux-install-${{ env.CACHE_DATE }}
 
     - name: cache-onnxruntime
       id: cache-onnxruntime
-      uses: actions/cache@v4
+      uses: actions/cache@v5
       with:
         path: onnxruntime-${{ env.ONNXRUNTIME_VERSION }}-install
         key: onnxruntime-${{ env.ONNXRUNTIME_VERSION }}-linux-install-${{ env.CACHE_DATE }}