Trying to optimize in such case breaks down the optimization, as we
end up with potentially non-eliminatable nodes that depend on the dead
IfTrue/IfFalse node.
Drive-by: Clean up dead nodes with {Kill()}.

Bug: v8:11510, chromium:1255354

Change-Id: Ia89fe6c243974c3c2abac6ad80bd4677a935f637
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3200073Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77211}