[SB][Wifi] Small cleanups of WifiRepositoryImplTest.

- Remove outdated doc
- Convert to mockito.kotlin
- Use UnconfinedTestDispatcher
- Remove runCurrents

Bug: EXEMPT test only
Flag: TEST_ONLY
Test: atest WifiRepositoryImplTest
Change-Id: I077d716cdd9169390ec8b5e6ac666a6814407518
1 file changed