OWNERS files: removed tebbi's entry.
TODOs: replaced with 'turbofan'.

Change-Id: Ib7a90418b394f123b82051379f120f0323d04097
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2639757Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Michael Hablich <hablich@chromium.org>
Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72223}