update tab icon to be consistent

Author: commit111

app/templates/index.html

@@ -5,7 +5,7 @@
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>Ask Defang</title>
     <script src="https://cdnjs.cloudflare.com/ajax/libs/marked/4.0.2/marked.min.js"></script>
-    <link rel="icon" href="{{ url_for('static', filename='images/defang_icon.svg') }}" type="image/svg">
+    <link rel="icon" href="{{ url_for('static', filename='images/favicon.ico') }}" type="image/x-icon">
     <style>
         @import url('https://fonts.googleapis.com/css2?family=Exo+2:ital,wght@0,100..900;1,100..900&display=swap');
     </style>