chore: remove pnpm devDependency (vitejs#11758)

Author: dominikg

package.json

@@ -76,7 +76,6 @@
     "npm-run-all": "^4.1.5",
     "picocolors": "^1.0.0",
     "playwright-chromium": "^1.29.2",
-    "pnpm": "^7.25.0",
     "prettier": "2.8.3",
     "prompts": "^2.4.2",
     "resolve": "^1.22.1",