The stack value is unused and does not need to be pushed or popped on
return from JSEntryTrampoline

Bug: 
Change-Id: I0e1920fc48b63cb0eea66454e5b74d9b3c2d5956
Reviewed-on: https://chromium-review.googlesource.com/650810
Commit-Queue: Caitlin Potter <caitp@igalia.com>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47849}