fix firestore session config example issue (#431)
fix firestore session config example issue (#431)

The Collection (kind) must be configured in the StoreOptions of the FirestoreStore and not in the settings of the Firestore.

https://github.com/googleapis/nodejs-firestore-session#using-the-client-library
GoogleCloudPlatform/nodejs-getting-started,GoogleCloudPlatform/nodejs-getting-started,GoogleCloudPlatform/nodejs-getting-started