parity_venv.sh follows the app to 3.13; the abi3 tag stays at cp312

The wheel is cp312-abi3, so it loads on 3.13 unchanged — the pin that has to
move is the interpreter the parity venv is built with, since its whole point is
resembling what the image ships.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CDYRXGB8tW4NE7b91g7Kdb

pyproject.toml

@@ -18,6 +18,7 @@ authors = [{ name = "N3XD" }]
 classifiers = [
     "Private :: Do Not Upload",
     "Programming Language :: Python :: 3.12",
+    "Programming Language :: Python :: 3.13",
     "Programming Language :: C++",
 ]