Bump actions/cache from 2 to 3

Bumps [actions/cache](https://github.com/actions/cache) from 2 to 3.
- [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/v2...v3)

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

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

.github/workflows/pio_build.yml

@@ -31,13 +31,13 @@ jobs:
       run: echo $PLATFORMIO_BUILD_FLAGS
     - uses: actions/checkout@v2
     - name: Cache pip
-      uses: actions/cache@v2
+      uses: actions/cache@v3
       with:
         path: ~/.cache/pip
         key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements.txt') }}
         restore-keys: ${{ runner.os }}-pip-
     - name: Cache PlatformIO
-      uses: actions/cache@v2
+      uses: actions/cache@v3
       with:
         path: ~/.platformio
         key: ${{ runner.os }}-${{ hashFiles('**/lockfiles') }}