Bump rlespinasse/github-slug-action from 4 to 5

Bumps [rlespinasse/github-slug-action](https://github.com/rlespinasse/github-slug-action) from 4 to 5.
- [Release notes](https://github.com/rlespinasse/github-slug-action/releases)
- [Commits](rlespinasse/github-slug-action@v4...v5)

---
updated-dependencies:
- dependency-name: rlespinasse/github-slug-action
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/unittest.yml

@@ -89,7 +89,7 @@ jobs:
         run: pip install --upgrade platformio
 
       - name: Inject slug/short variables
-        uses: rlespinasse/github-slug-action@v4
+        uses: rlespinasse/github-slug-action@v5
 
       - name: Run PlatformIO and compile sketch
         id: compile_sketch