chore: Update OWNERS for accessibility dirs.

- Add LV members to the magnification subdir.
- Use the test component for OWNERS files, since this
  component is only used when automation files test bugs.

Bug: none
Test: n/a OWNERS only
Flag: EXEMPT OWNERS only
Change-Id: I71a6d834f3c33a97be5d9ac4fb5e6d54e5dd473e