Fix typo in auth section (#80)

Author: danroth27

docs/4. Add auth features.md

@@ -176,7 +176,7 @@ In this module we're going to add the capability for users to register and sign-
     ``` c#
     public bool AllowAdminCreation { get; set; }
     ```
-1. Add a `bool` property to to the page's `InputModel` class to capture when the incoming request wants to attempt to create an admin user:
+1. Add an `AdminCreationKey` property to to the page's `InputModel` class to capture the submitted key for creating the admin user:
     ``` c#
     [DataType(DataType.Password)]
     [Display(Name = "Admin creation key")]