github: hello_world_multiplatform: set --runtime-artifact-cleanup

Set --runtime-artifact-cleanup on the twister run to reduce the disk
usage of the workflow.

Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>

Author: fabiobaltieri

.github/workflows/hello_world_multiplatform.yaml

@@ -70,7 +70,7 @@ jobs:
           elif [ "${{ runner.os }}" = "Windows" ]; then
             EXTRA_TWISTER_FLAGS="-P native_sim --short-build-path -O/tmp/twister-out"
           fi
-          ./scripts/twister --force-color --inline-logs -T samples/hello_world -T samples/cpp/hello_world -v $EXTRA_TWISTER_FLAGS
+          ./scripts/twister --runtime-artifact-cleanup --force-color --inline-logs -T samples/hello_world -T samples/cpp/hello_world -v $EXTRA_TWISTER_FLAGS
 
       - name: Upload artifacts
         if: failure()