Fix lint issues in IMMS

Bug: 238470908
Test: m
Test: atest InputMethodManagerServiceTests
Test: prebuilts/checkstyle/checkstyle.py -f frameworks/base/services/core/java/com/android/server/inputmethod/ | grep ".java:" | grep InputMethodManagerService
Change-Id: Ic07ab4f496f954f2f079f2216f0d1d585275e10a