Updated enrollUser function in write_first_app Doc (#2713)

Signed-off-by: becomingmountains <jstaffordcoyte@gmail.com>
(cherry picked from commit 73c46a1)

docs/source/write_first_app.rst

@@ -293,7 +293,7 @@ to interact with the blockchain network. The section of the application code is
 
   // in a real application this would be done only when a new user was required to be added
   // and would be part of an administrative flow
-  await registerUser(caClient, wallet, userId, 'org1.department1');
+  await registerAndEnrollUser(caClient, wallet, mspOrg1, org1UserId, 'org1.department1');
 
 Similar to the admin enrollment, this function uses a CSR to register and enroll ``appUser`` and
 store its credentials alongside those of ``admin`` in the wallet. We now have