Reduce Flakiness for VisualQueryDetection file read

The test leverages IPC to send out read result from the isolated process. The previous value would create 1000 transactions for the binder call which can lead to buffer full and allocation failure even though that amount of files can be read. Reduce it to 50 as checked in drivers/android/binder_alloc.c for less flakiness.

Bug: 289185455
Test: atest CtsVoiceInteractionTestCases
Change-Id: Ice0c560c5ad355e06c4f5d2ffb56f8f3ddcfd52d
Merged-In: Ice0c560c5ad355e06c4f5d2ffb56f8f3ddcfd52d