Remove Google Assistant from FGS while-in-use restriction white list.

The system server binding to VoiceInteractionService with BIND_INCLUDE_CAPABILITIES flag,
already gives assistant all capabilities.

Bug: 150893575
Test: atest cts/tests/app/src/android/app/cts/ActivityManagerProcessStateTest.java
Change-Id: I26ef5cdfc78abc7930b727c6efce89cad0dfe3e4