Fix "ActivityTaskManager.requestAssistDataForTask crash on secondary user"

I only tested the VoiceInteractionService codepath and didn't realize
the Launcher also depends on the assist data API.
The VIS code path has cleared the caller identity before calling into
isAssistDataAllowed. However, requestAssistDataForTask does not.

Test: Create a secondary user. Open an app. Go to the overview screen.
Without the fix, crash observed. With the fix, no more crash.
Test: atest android.voiceinteraction.cts.VoiceInteractionServiceTest

Fixes: 323909861
Change-Id: I59b6e2de9cc3616b0867b128403ff0c4514eb905