Enable restat for kapt stubs rules

The output of the kapt stubs rules only change when the public interface
of a kotlin class changes, which makes them a good candidate for restat.
This will prevent some unnecessary reruns of turbine annotation
processing.

Bug: 297356926
Test: builds
Change-Id: I39bd63284fd37058f69a0a3dace1ea5f4f50e8b5