Revert "Define FeatureFlagsService."

Revert submission 23727772-b279054964-flag-api-udc-qpr-dev

Reason for revert: b/290929382

Reverted changes: /q/submissionid:23727772-b279054964-flag-api-udc-qpr-dev

Change-Id: I144a92ee478b76d98dc1a2a47533cb524c5fc056
23 files changed