audio/pipewire-spa-oss-ng: Update to 0.9.3

Fixes a field report of periodic drops with crackles on USB audio: the
sink's near-full fill branch keyed on small driver-forced fragments as a
proxy for a small total buffer, which uaudio breaks (1 ms soft fragments,
large grant) - near-full targeting added 100+ ms of latency and left one
fragment of overshoot headroom, so every normal servo excursion
short-wrote and dropped the tail.

Validated by a discrete-event simulation of the servo (exact DLL and
bandwidth-adaptation ports) that reproduces the field failure with the
old target and shows zero drops with the new one across +/-2000 ppm
drift, jitter storms and 4-hour runs, plus the live battery on hdspe(4).