fix(package): update firebase to version 7.2.2

Closes #220

Author: greenkeeper[bot]

package.json

@@ -15,7 +15,7 @@
     "expo-font": "^5.0.1",
     "expo-permissions": "^5.0.1",
     "expo-web-browser": "^5.0.3",
-    "firebase": "^6.1.1",
+    "firebase": "^7.2.2",
     "moment": "^2.24.0",
     "react": "16.8.3",
     "react-native": "https://github.com/expo/react-native/archive/sdk-33.0.0.tar.gz",