fix: remove obsolete package and fix tests

packages/app/package.json

@@ -18,7 +18,6 @@
     "@material-ui/core": "^4.9.1",
     "@material-ui/icons": "^4.9.1",
     "@material-ui/lab": "4.0.0-alpha.45",
-    "@types/http-proxy": "^1.17.4",
     "prop-types": "^15.7.2",
     "react": "^16.12.0",
     "react-dom": "^16.12.0",