Update README.md for providers. (#56)

Author: laurenzlong

src/providers/README.md

@@ -3,7 +3,7 @@ Check out [the Cloud Functions for Firebase documentation](https://firebase.goog
 
 ### The `datastore` provider
 The Datastore integration is in early preview, and not yet publicly usable.
-If you'd like to request early access to use this integration, [please fill out this form](https://goo.gl/forms/6T2kHu7n4N5IB7Ya2).
+If you'd like to request early access to use this integration, [please fill out this form](https://services.google.com/fb/forms/firebasealphaprogram/).
 
 Since this is a preview feature, any new version may introduce breaking changes.
 It is recommended that you depend on a specific version of the firebase-functions SDK