Increase RBE usage for ART tests to 40% am: 5e6497275c am: e785d0f065 am: 1583915a21 am: 76126f1cd3

Original change: https://android-review.googlesource.com/c/platform/art/+/2167662

Change-Id: Iddcb5683fa9eee5849e9478d20c05f72a800cdb5
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>