flags: remove translate flags & update metadata

This change removes these flags:
  translate
  translate-explicit-ask
  translate-ranker-enforcement
All the backing base::Features remain for controllability via Finch.

This change adds owners and an expiration date for this flag:
  translate-force-trigger-on-english

This change also marks this flag as never-expiring:
  translate-android-manual-trigger
This flag is used for QA purposes on Android where there is no other QA
configuration mechanism.

Bug: None
Change-Id: I7ad74d7432627edc6dc141952c0d598e7dbfdba0
Reviewed-on: https://chromium-review.googlesource.com/c/1468025
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: anthonyvd <anthonyvd@chromium.org>
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#632273}
4 files changed