ci: clang: Remove obsolete clean-up steps

The repository clean-up steps are no longer necessary because the new
zephyr-runner is ephemeral and does not contain any files from the
previous runs.

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>

.github/workflows/clang.yaml

@@ -34,11 +34,6 @@ jobs:
           #        GitHub comes up with a fundamental fix for this problem.
           git config --global --add safe.directory ${GITHUB_WORKSPACE}
 
-      - name: Cleanup
-        run: |
-          # hotfix, until we have a better way to deal with existing data
-          rm -rf zephyr zephyr-testing
-
       - name: Clone cached Zephyr repository
         continue-on-error: true
         run: |