Bump actions/cache from 4 to 5

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] <[email protected]>

Author: dependabot[bot]

.github/workflows/docs.yml

@@ -31,7 +31,7 @@ jobs:
 
       - name: Restore TorchIO cached data
         id: cache-torchio-data-restore
-        uses: actions/cache/restore@v4
+        uses: actions/cache/restore@v5
         with:
           path: ~/.cache/torchio
           key: ${{ runner.os }}-torchio-data
@@ -42,7 +42,7 @@ jobs:
       - name: Save TorchIO cached data
         if: steps.cache-torchio-data-restore.outputs.cache-hit != 'true'
         id: cache-torchio-data-save
-        uses: actions/cache@v4
+        uses: actions/cache@v5
         with:
           path: ~/.cache/torchio
           key: ${{ steps.cache-torchio-data-restore.outputs.cache-primary-key }}