Remove useless V8 default GN args.

Support for v8_extra_library_files and
v8_experimental_extra_library_files got removed as part of
crbug.com/v8/7624 over 2 years ago.

Change-Id: I5bb7e38dc90a99def4ea627b18c5240c808f233f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3615256


Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Cr-Commit-Position: refs/heads/main@{#999978}