Fix icon in Web App 9 and 10 templates (#4337)

Author: vnbaaij

src/Templates/templates/blazorweb-csharp-10/BlazorWebCSharp.1/Components/App.razor

@@ -10,7 +10,7 @@
     <link rel="stylesheet" href="@Assets["BlazorWebCSharp.1.styles.css"]" />
     <ImportMap />
     @*#if (SampleContent)
-    <link rel="icon" type="image/png" href="favicon.png" />
+    <link rel="icon" type="image/x-icon" href="favicon.ico" />
     ##endif*@
     @*#if (!InteractiveAtRoot)
     <HeadOutlet />

src/Templates/templates/blazorweb-csharp-9/BlazorWeb-CSharp/Components/App.razor

@@ -9,7 +9,7 @@
     <link rel="stylesheet" href="@Assets["BlazorWeb-CSharp.styles.css"]" />
     <ImportMap />
     @*#if (SampleContent)
-    <link rel="icon" type="image/png" href="favicon.png" />
+    <link rel="icon" type="image/x-icon" href="favicon.ico" />
     ##endif*@
     @*#if (!InteractiveAtRoot)
     <HeadOutlet />