Full GCs on non-main-frame context disposals show up on real-world web
workloads and often cause missed frames. Remove and let the regular
scheduler take over these workloads.

Bug: chromium:1191325
Change-Id: Ib58419e4623c096321860db05c36ddf9c8e9f4e4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2773347
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73799}