This removes the test suite variant for stressing Crankshaft from the
list of supported variants. Other stress variants remain untouched.

R=machenbach@chromium.org

Cq-Include-Trybots: master.tryserver.v8:v8_linux_noi18n_rel_ng
Change-Id: Iad236c2b80a1dea21b8be9b931e6a4e88f3ebcc5
Reviewed-on: https://chromium-review.googlesource.com/527094Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45758}