[iOS]Fix Unlock and Cancel buttons not shown when creating new private tab (#34382)

Fix Unlock and Cancel buttons not shown when creating new private tab with lock enabled

When "Require Touch ID/Face ID" was enabled for private tabs, the Unlock and Cancel buttons were hidden when creating a new private tab via the + button and cancelling the biometric prompt.

- Always show Unlock button when auth fails so user can retry
- Set isCancellable=true for non-external view types to show Cancel button

Signed-off-by: Eli Hini <8249954+EliHini@users.noreply.github.com>

ios/brave-ios/Sources/Brave/Frontend/Passcode/WindowProtection.swift

@@ -235,9 +235,7 @@ public class WindowProtection {
     }
 
     lockedViewController.unlockButton.isHidden = true
-    if viewType == .external {
-      isCancellable = false
-    }
+    isCancellable = viewType != .external
 
     context.evaluatePolicy(
       .deviceOwnerAuthentication,
@@ -257,7 +255,7 @@ public class WindowProtection {
             }
           )
         } else {
-          lockedViewController.unlockButton.isHidden = viewType == .general
+          lockedViewController.unlockButton.isHidden = false
 
           let errorPolicy = error as? LAError
           completion?(false, errorPolicy?.code)