Address AnrTimer minor review comments

This CL address two review comments from an earlier commit:
 1. The call to register_android_server_utils_AnrTimer() is now
    sorted, per the style guide.
 2. An iterator error is fixed in AnrTimerService::Ticker::remove().

Test: atest
 * FrameworksServicesTests:com.android.server.am
 * FrameworksMockingServicesTests:com.android.server.am
 * CtsAppTestCases
 * FrameworksServicesTests:AnrTimerTest

Bug: 282428924
Change-Id: Id35076ae4f477330c455275f502ab39b2265745a