Freeze stylex version

Author: tomchochola

package.json

@@ -35,7 +35,7 @@
     "@babel/preset-env": "^7.26.9",
     "@babel/preset-react": "^7.26.3",
     "@babel/preset-typescript": "^7.27.0",
-    "@stylexjs/babel-plugin": "latest",
+    "@stylexjs/babel-plugin": "^0.12.0",
     "babel-plugin-react-compiler": "^19.1.0-rc.1",
     "core-js": "^3.41.0"
   },