Replace OVERRIDE with its C++11 counterpart in components/password_manager/

This CL replaces |OVERRIDE| with |override| as per allowed C++11 features.
|FINAL| is already not used in components/password_manager/

BUG=417463

Review URL: https://codereview.chromium.org/611383002

Cr-Commit-Position: refs/heads/master@{#297600}
24 files changed