fix: fixtures/nesting/package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-CSSWHAT-1298035
- https://snyk.io/vuln/SNYK-JS-POSTCSS-5926692
- https://snyk.io/vuln/SNYK-JS-SEMVER-3247795
- https://snyk.io/vuln/SNYK-JS-TOUGHCOOKIE-5672873

fixtures/nesting/package.json

@@ -3,7 +3,7 @@
   "version": "0.1.0",
   "private": true,
   "dependencies": {
-    "react-scripts": "3.4.1",
+    "react-scripts": "5.0.0",
     "redux": "^4.0.5"
   },
   "scripts": {