Most Liftoff code comments are generated by the {NextInstruction}
function. That code was inside an "#ifdef DEBUG" block so far, because
previously code comments were only enabled in debug builds anyway. Now
that we have the separate v8_code_comments gn arg, they can also be
enabled in release builds.
Hence remove the "#if DEBUG" such that code comments are also output in
release mode.

This should not introduce any compile time regressions since both macros
are no-ops in official builds.

R=ahaas@chromium.org

Change-Id: I0bdd11534620072ccf0ff959c7f7d658aa75717b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2985243
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75382}