Update nullable annotations

src/Microsoft.AspNetCore.Razor.Language/src/AssemblyExtension.cs

@@ -1,8 +1,6 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-#nullable disable
-
 using System;
 using System.Reflection;
 
@@ -30,7 +28,7 @@ public AssemblyExtension(string extensionName, Assembly assembly)
 
     public Assembly Assembly { get; }
 
-    internal RazorExtensionInitializer CreateInitializer()
+    internal RazorExtensionInitializer? CreateInitializer()
     {
         // It's not an error to have an assembly with no initializers. This is useful to specify a dependency
         // that doesn't really provide any Razor configuration.

src/Microsoft.AspNetCore.Razor.Language/src/AttributeStructure.cs

@@ -1,8 +1,6 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-#nullable disable
-
 namespace Microsoft.AspNetCore.Razor.Language;
 
 // This is the design time equivalent of Microsoft.AspNetCore.Razor.TagHelpers.HtmlAttributeValueStyle.

src/Microsoft.AspNetCore.Razor.Language/src/CSharpIdentifier.cs

@@ -1,8 +1,6 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-#nullable disable
-
 using System.Globalization;
 using System.Text;
 

src/Microsoft.AspNetCore.Razor.Language/src/Checksum.cs

@@ -1,8 +1,6 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-#nullable disable
-
 using System;
 using System.Globalization;
 using System.Text;