fix: packages/app/package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-MINDOCUMENT-13045385

Author: snyk-bot

packages/app/package.json

@@ -208,7 +208,7 @@
     "react-helmet": "^6.1.0",
     "react-icons": "^2.2.7",
     "react-input-autosize": "^2.2.1",
-    "react-instantsearch": "^5.7.0",
+    "react-instantsearch": "^6.0.0",
     "react-loadable": "^3.3.1",
     "react-markdown": "^5.0.0",
     "react-media": "^1.10.0",