chore: remove authViewRoutes as can access navigator directly

Author: russellwheatley

FirebaseSwiftUI/FirebaseAuthSwiftUI/Sources/Services/AuthService.swift

@@ -123,14 +123,11 @@ public final class AuthService {
   public let auth: Auth
   public var isPresented: Bool = false
   public private(set) var navigator = Navigator()
+  
   public var authView: AuthView? {
     navigator.routes.last
   }
 
-  var authViewRoutes: [AuthView] {
-    navigator.routes
-  }
-
   public let string: StringUtils
   public var currentUser: User?
   public var authenticationState: AuthenticationState = .unauthenticated