test: fix example test

Author: azu

example/package.json

@@ -14,7 +14,7 @@
   "license": "MIT",
   "devDependencies": {
     "@textlint/website-generator": "^0.11.3",
-    "textlint": "^12.0.0-beta.2"
+    "textlint": "^12.0.0"
   },
   "dependencies": {
     "textlint-rule-preset-jtf-style": "file:.."

package.json

@@ -28,7 +28,7 @@
     "prepublish": "npm run --if-present build",
     "pretest": "node tool/create-fixtures.js",
     "test": "textlint-scripts test && npm run test:textlint",
-    "test:textlint": "(cd example && npm i --no-save && npm test)",
+    "test:textlint": "(cd example && yarn && npm test)",
     "format": "prettier --write \"**/*.{js,jsx,ts,tsx,css}\"",
     "prepare": "git config --local core.hooksPath .githooks"
   },