[dotnet] Add future-proofing note on Base64UrlEncoder (#14821)

Author: RenderMichael

dotnet/src/webdriver/Internal/Base64UrlEncoder.cs

@@ -19,8 +19,17 @@
 
 using System;
 
+#nullable enable
+
 namespace OpenQA.Selenium.Internal
 {
+    /*
+     * Based on: https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/blob/6.19.0/src/Microsoft.IdentityModel.Tokens/Base64UrlEncoder.cs
+     * 
+     * Now it is a part of .NET 9+ as System.Buffers.Text.Base64Url
+     * https://github.com/SeleniumHQ/selenium/issues/14813  
+     */
+
     /// <summary>
     /// Encodes and Decodes strings as Base64Url encoding.
     /// </summary>
@@ -45,8 +54,6 @@ public static class Base64UrlEncoder
             base64UrlCharacter63
         };
 
-        // https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/blob/6.19.0/src/Microsoft.IdentityModel.Tokens/Base64UrlEncoder.cs#L85
-
         /// <summary>
         /// Converts a subset of an array of 8-bit unsigned integers to its equivalent string representation which is encoded with base-64-url digits.
         /// </summary>
@@ -115,8 +122,6 @@ public static string Encode(byte[] inArray)
             return new string(output, 0, j);
         }
 
-        // https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/blob/6.19.0/src/Microsoft.IdentityModel.Tokens/Base64UrlEncoder.cs#L179
-
         /// <summary>
         ///  Converts the specified string, which encodes binary data as base-64-url digits, to an equivalent 8-bit unsigned integer array.</summary>
         /// <param name="str">base64Url encoded string.</param>