fix: example/package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-BROWSERSLIST-1090194
- https://snyk.io/vuln/SNYK-JS-IMMER-1540542
- https://snyk.io/vuln/SNYK-JS-PROMPTS-1729737
- https://snyk.io/vuln/SNYK-JS-SHELLQUOTE-1766506

example/package.json

@@ -17,7 +17,7 @@
     "gatsby-theme-mate": "0.0.0",
     "react": "^17.0.2",
     "react-dom": "^17.0.2",
-    "gatsby": "^4.0.0"
+    "gatsby": "^4.14.0"
   },
   "devDependencies": {
     "@percy/cli": "^1.0.0-beta.63",