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

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-CROSSSPAWN-8303230

packages/demo/package.json

@@ -11,12 +11,12 @@
     "postinstall": "expo-yarn-workspaces postinstall"
   },
   "dependencies": {
-    "expo": "^45.0.0",
+    "expo": "^49.0.0",
     "react": "16.8.3",
     "react-dom": "^16.8.6",
     "react-native": "https://github.com/expo/react-native/archive/sdk-33.0.0.tar.gz",
     "react-native-debug-console": "^2.0.0-alpha.17",
-    "react-native-web": "0.15.0"
+    "react-native-web": "0.11.4"
   },
   "devDependencies": {
     "@babel/runtime": "^7.5.0",