Loosen misaki[en] pin so pip install kokoro resolves (fixes #321)

[chiddekel]

Problem

pip install kokoro can fail with:

ERROR: Could not find a version that satisfies the requirement misaki>=0.9.x
ERROR: No matching distribution found for misaki>=0.9.x

kokoro bumps the misaki[en] floor to its own version number on every release (currently misaki[en]>=0.9.4). Because kokoro and misaki are published separately, any window where kokoro lands on PyPI before the matching misaki makes the package un-installable from PyPI alone — even into a fresh venv. This is exactly the failure in #321 (it hit 0.7.16 → misaki 0.7.4; the same trap recurs every release).

Fix

Relax the pin from misaki[en]>=0.9.4 to misaki[en]>=0.9.2 — a one-line change.

Why this is safe:

• The API floor is far below the pin. kokoro only uses en.G2P, espeak.EspeakFallback/EspeakG2P, ja.JAG2P, and zh.ZHG2P(version=..., en_callable=...). That surface was last matched to misaki 0.8.0 (commit efa91a8, "Match misaki==0.8.0 dev branch") and hasn't changed since — so the exact-version lockstep is unnecessary.
• No quality regression. pip/uv still selects the newest available misaki (resolves to 0.9.4 today); 0.9.2 only acts as a fallback during the publish gap, and stays within the 0.9 minor for phoneme/data parity.
• Consistent with the lockfile. uv.lock already pins misaki at 0.9.2 with specifier = ">=0.9.2", so this aligns pyproject.toml with what the repo already resolves.

Reproduction (from the issue)

python3 -m venv /tmp/test
/tmp/test/bin/pip install kokoro   # failed when misaki lagged kokoro

Fixes #321