API feedback: remove callback for VisualQueryDetectionService

We may not like the design to send things back to the system server
with callback since VisualQueryDetectionService does not perform
per-session based detection on external signals.

Bug: 266564316
Test: atest CtsVoiceInteractionTestCases
Change-Id: I3ea140902bb83645f5dc5d3bcc0af0b3232f74b1