All use cases of the RecursiveMutex have been removed.

Bug: v8:6923
Change-Id: I25aeee2447db185dbaacf96ab06a660834a408b7
Reviewed-on: https://chromium-review.googlesource.com/735345Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48908}