Fix build error in unit tests by updating NavigateToEnterAccount.init.

Author: jaclync

WordPressAuthenticatorTests/Navigation/NavigationToEnterAccountTests.swift

@@ -6,7 +6,7 @@ final class NavigationToAccountTests: XCTestCase {
         let origin = UIViewController()
         let navigationController = MockNavigationController(rootViewController: origin)
 
-        let command = NavigateToEnterAccount()
+        let command = NavigateToEnterAccount(signInSource: .wpCom)
         command.execute(from: origin)
 
         let pushedViewController = navigationController.pushedViewController