Merge pull request scratchfoundation#4985 from LLK/greenkeeper/react-modal-3.9.1

Update react-modal to the latest version 🚀

Author: benjiwheeler

package-lock.json

@@ -91,7 +91,7 @@
     "react-draggable": "3.0.5",
     "react-ga": "2.5.3",
     "react-intl": "2.9.0",
-    "react-modal": "3.6.1",
+    "react-modal": "3.9.1",
     "react-popover": "0.5.10",
     "react-redux": "5.0.7",
     "react-responsive": "5.0.0",