Increase delay time for ScanManagerTest

ScanManagerTest#testMetricsScanRadioDuration is currently flaky due to
delay in rare long delays in start and stop scan calls. The test
measures duration of scan and takes into account the delay that may
happen in test situations, but the delay needs to be increased to cover
some very rare test failures due to long delays.

Bug: 323290726
Test: atest BluetoothInstrumentationTests
Flag: EXEMPT, test change only
Change-Id: I278133f6526bb400932b95a92941823d7f9e70ba