This is a follow-up to https://crrev.com/c/3015557. Even though we
enabled trap handling and use it in wasm code, the embedder callback
still refused to handle the signal.
This CL removed an obsolete comment and simplifies the preprocessor
condition to just check for the V8_TRAP_HANDLER_SUPPORTED variable
instead of repeating the supported platforms.

R=ahaas@chromium.org

Bug: v8:11955, chromium:1231858
Change-Id: I417c790fdb755cba182578e7aa1ce4327f4c05ef
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3045352Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75860}