We now always tier down to Liftoff when the debugger is enabled, hence
we don't need to force Liftoff-only execution in the test.

R=thibaudm@chromium.org
CC=duongn@microsoft.com

Bug: v8:9654
Change-Id: I9b9e21b2ee977b349bb4f5d0e34c6ebf82166cb9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2093504Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66630}