Switch the flag to true to enable ArrayBufferExtensions by default.

Bug: v8:10064
Change-Id: I9b772fbd36372e3454ac66a476d33cba121b45c9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2064208Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66339}