release: roll WASM Zone OOM fix into 0.9.3 (not 0.9.4) (#323)

0.9.3 was prepped in the repo but never released (latest published is
0.9.2), so the turboshaft WASM Zone OOM fix ships as part of 0.9.3.
Fold its changelog entry into [0.9.3] and revert the version bump.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>