Remove root target preparer from ART run-tests configuration template.

This is no longer needed since ART run-tests use paths under
`/data/local/tmp/` on device that do not require root permissions.

Test: atest --test-mapping art:postsubmit
Bug: 147814778
Bug: 147812905
Change-Id: I0f31b5d35c0777571f6f50ad9d55735845d890e8
1 file changed