Check for origin mismatch before displaying mixed content warning

This fixes a bug where navigating back/forward between NTP & web pages may show 'not secure' on NTP for a brief moment

Sources/Brave/Frontend/Browser/BrowserViewController.swift

@@ -1770,7 +1770,8 @@ public class BrowserViewController: UIViewController {
         break
       }
 
-      if tab.secureContentState == .secure && !webView.hasOnlySecureContent {
+      if tab.secureContentState == .secure, !webView.hasOnlySecureContent,
+         tab.url?.origin == tab.webView?.url?.origin {
         if let url = tab.webView?.url, url.isReaderModeURL {
           break
         }