Fix integer overflow for audio packet duration

The result is assigned to a long (64-bit signed integer), but the
intermediate multiplication was stored in an int (32-bit signed
integer).

This value is only used as a fallback when no timestamp could be
retrieved, that's why it did not cause too much harm so far.

Fixes #4536 <https://github.com/Genymobile/scrcpy/issues/4536>

server/src/main/java/com/genymobile/scrcpy/AudioCapture.java

@@ -159,7 +159,7 @@ public final class AudioCapture {
             pts = nextPts;
         }
 
-        long durationUs = r * 1000000 / (CHANNELS * BYTES_PER_SAMPLE * SAMPLE_RATE);
+        long durationUs = r * 1000000L / (CHANNELS * BYTES_PER_SAMPLE * SAMPLE_RATE);
         nextPts = pts + durationUs;
 
         if (previousPts != 0 && pts < previousPts + ONE_SAMPLE_US) {