[SB] Delete StatusBarModePerDisplayRepository#clearTransient

After If3fa61005f7905bb541743e61ec20a6c8cf8a1f5, #clearTransient is no
longer called so we can remove it.

Bug: 312137467
Flag: EXEMPT bugfix
Test: atest StatusBarOrchestratorTest StatusBarModeRepositoryImplTest
Change-Id: I25dcdf0d2c19f0dc975046d7888ef6abb667aa7f
4 files changed