Retire TextUnderlinePositionLeftRight flag

'left' and 'right' values for the 'text-underline-position' property
shipped in M71.
https://www.chromestatus.com/features/5749634488074240

The flag TextUnderlinePositionLeftRight has been enabled since
https://chromium-review.googlesource.com/1226485

BUG=313888

Change-Id: I893bbc0d402439a092c96d39b629dd8c94627622
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1616832
Reviewed-by: Koji Ishii <kojii@chromium.org>
Commit-Queue: Eric Willigers <ericwilligers@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661316}
2 files changed