Fix remaining lint erros under a.i.navigationbar

This is a mechanical cleanup CL.  There should be no behavior change.

Bug: 215443343
Test: prebuilts/checkstyle/checkstyle.py -f \
  frameworks/base/core/java/android/inputmethodservice/navigationbar/ \
  | grep ".java:"
Change-Id: Ib9dcddc675bdd540ae93a1eb5b1db00d1dccecb1