Clean up after ourselves in the Rust Benchmark Template

There's a compliance check for tradefed that ensures that configs for
tests are set to cleanup after themselves. See: https://cs.android.com/android/platform/superproject/main/+/main:tools/tradefederation/core/javatests/com/android/tradefed/presubmit/GeneralTestsConfigValidation.java;l=425-429;drc=1fb7fe35bf7c843b5bac510476d63e4c8b436a48

This causes new benchmarks to fail presubmits.

Test: CLs with rust benchmarks pass presubmits now
Change-Id: I14f64ee3343bcf9bd2d77f547dc16b9c15bf4082