ime-service: Delete InputEngine.ProcessText.

It is deprecated and no longer used.

Bug: 1009903
Change-Id: I6774a4506bd0bb41a5d1a5909a40a2a781564b16
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1833029
Auto-Submit: Darren Shen <shend@chromium.org>
Reviewed-by: Chris Palmer <palmer@chromium.org>
Reviewed-by: Keith Lee <keithlee@chromium.org>
Reviewed-by: Shu Chen <shuchen@chromium.org>
Commit-Queue: Darren Shen <shend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#705445}
InputEngine::InputEngine() {}

InputEngine::InputEngine() {}
