If v8_enable_runtime_call_stats == false, we don't need
TracingFlags::is_runtime_stats_enabled and can save a bit of code and
needless overhead.

Bug: v8:11299
Change-Id: Ia5ec51c29b2408b77b65984c5bba0ae16e0de243
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3024155Reviewed-by: Patrick Thier <pthier@chromium.org>
Reviewed-by: Mythri Alle <mythria@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75983}