flags: remove disable-hyperlink-auditing

This flag controls a feature that has been on by default for nearly a decade
now.

Bug: 935978
Change-Id: I506194c49389df0c4d59096f1b2c14d8ca6eee9f
Reviewed-on: https://chromium-review.googlesource.com/c/1489131
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Mike West <mkwst@chromium.org>
Auto-Submit: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Mike West <mkwst@chromium.org>
Cr-Commit-Position: refs/heads/master@{#635515}