All architectures have kSupportsFixedDeoptExitSizes = true, so we can
remove kSupportsFixedDeoptExitSizes entirely and always have fixed-size
deopts.

Change-Id: Ib696f6d2431f60677cc7fa2193ee27b9b0f80bc8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3550268Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79654}