docs: Update auth0.md (#3566)

Author: jdanielnd

docs/cookbook/authentication/auth0.md

@@ -40,7 +40,7 @@ In `src/authentication.ts` like this:
 import { ServiceAddons, Params } from '@feathersjs/feathers';
 import { AuthenticationService, JWTStrategy } from '@feathersjs/authentication';
 import { LocalStrategy } from '@feathersjs/authentication-local';
-import { expressOauth, OAuthStrategy, OAuthProfile } from '@feathersjs/authentication-oauth';
+import { oauth, OAuthStrategy, OAuthProfile } from '@feathersjs/authentication-oauth';
 
 import { Application } from './declarations';
 
@@ -69,7 +69,7 @@ export default function(app: Application) {
   authentication.register('auth0', new Auth0Strategy());
 
   app.use('/authentication', authentication);
-  app.configure(expressOauth());
+  app.configure(oauth());
 }
 ```