fix: client/package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-NODENOTIFIER-1035794
- https://snyk.io/vuln/SNYK-JS-OBJECTPATH-1017036

Author: snyk-bot

client/package.json

@@ -11,7 +11,7 @@
     "react-dom": "^16.7.0",
     "react-redux": "^6.0.0",
     "react-router": "^4.3.1",
-    "react-scripts": "3.4.3",
+    "react-scripts": "4.0.0",
     "recharts": "^1.4.2",
     "redux": "^4.0.1",
     "redux-saga": "^0.16.2"