Bump the github-actions group with 1 update

Bumps the github-actions group with 1 update: [actions/cache](https://github.com/actions/cache).


Updates `actions/cache` from 3 to 4
- [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/v3...v4)

---
updated-dependencies:
- dependency-name: actions/cache
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: github-actions
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/test.platformio.yml

@@ -33,13 +33,13 @@ jobs:
     steps:
     - uses: actions/checkout@v4
     - name: Cache pip
-      uses: actions/cache@v3
+      uses: actions/cache@v4
       with:
         path: ~/.cache/pip
         key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements.txt') }}
         restore-keys: ${{ runner.os }}-pip-
     - name: Cache PlatformIO
-      uses: actions/cache@v3
+      uses: actions/cache@v4
       with:
         path: ~/.platformio
         key: ${{ runner.os }}-${{ hashFiles('**/lockfiles') }}