Remove translation service feature.

Currently, the Translation uses feature to determine if we need to
start the translation system service. But our case is like the
content capture not the autofill, the autofill can have the feature
without any service defined and the user can install one later. But
translation isn't, we should need to check config instead of
feature.

The feature will not be used anymore, it's safe to delete it. If we
leave the removal to next OS, it is painful to delete it.

Bug: 183360041
Test: atest CtsTranslationTestCases

Change-Id: Ib6886a17965937abf064e526c36c67428af7398f