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

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-ANSIREGEX-1583908

packages/demo/package.json

@@ -11,7 +11,7 @@
     "postinstall": "expo-yarn-workspaces postinstall"
   },
   "dependencies": {
-    "expo": "^34.0.1",
+    "expo": "^39.0.1",
     "react": "16.8.3",
     "react-dom": "^16.8.6",
     "react-native": "https://github.com/expo/react-native/archive/sdk-33.0.0.tar.gz",