Remove flags that are not used any more.

R=mstarzinger@chromium.org

Bug: v8:7109
Change-Id: I2c456f0e250688bd4cf57ccb3f0f8237fdc2ec58
Reviewed-on: https://chromium-review.googlesource.com/805954Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49839}