defaults: pulse: Reduce fragment size to 22 ms

Turns out that having the fragment size be larger than 22 ms
triggers a bug in Waydroid breaking it audio. Since this is
a balance between latency and possibility of underruns
occuring, let's reduce the recently bumped fragment size by
a tiny bit to make Waydroid happy, resulting in latency lowered
by 4 ms as a bonus.