[flexiglass] Cleanup {Password|Pattern|Pin}BouncerViewModelTest

Cleaning up the redundant "kosmos." prefixes that I added as part of http://ag/c/platform/frameworks/base/+/33533127/comment/3e5a43b5_be781c45/.

Bug: none
Flag: EXEMPT - test refactor
Test: atest PasswordBouncerViewModelTest PatternBouncerViewModelTest PinBouncerViewModelTest
Change-Id: I10be58973ddcc2c08585a0f91bb02ab053c671ad