audiotrack_tests: Reduce wait time during playback

In static buffer mode, during playback, the test yields for a
large duration. As the test clips are of small duration, the
playback finishes during this wait. Reduce this wait period
to improve code coverage.

Bug: 254222780
Test: atest audiotrack_tests

Change-Id: I24dfb90b207d0f4017e99112b1b50e322ab3428e