Allow adding favorites when a bookmark already exists (#1258)

Task/Issue URL: https://app.asana.com/0/1177771139624306/1203568202955279/f
Tech Design URL:
CC:

Description:

This PR simplifies the Add/Edit Favorite view controller logic. Before this PR, if you opened up this view controller and entered a URL for a bookmark that already existed, it wouldn't let you do anything. Now it will update that bookmark with the new title (if it has changed) and favourite it.

Author: samsymons

DuckDuckGo/HomePage/View/AddEditFavoriteViewController.swift

@@ -99,11 +99,7 @@ final class AddEditFavoriteViewController: NSViewController {
 
     private var isInputValid: Bool {
         guard let url = urlInputTextField.stringValue.url else { return false }
-        let isBookmarked = bookmarkManager.isUrlBookmarked(url: url)
-        let isInputValid = !titleInputTextField.stringValue.isEmpty &&
-            url.isValid &&
-        (!isBookmarked || url.absoluteString == originalBookmark?.url)
-        return isInputValid
+        return !titleInputTextField.stringValue.isEmpty && url.isValid
     }
 
     private func updateConfirmButton() {