Delete dead test SettingsActivityTest

Settings activity tests are UI heavy, so unlikely anyone would fix this
such that they are not flaky.

These tests are @Ignored for long time (> 1 year).

Bug: 199309785
Test: presubmit
Flag: NONE not a change in production code
Change-Id: I8c9e167469266af624ae345e8eaac8bb92e8cd69