Implement Authorizations Delete method with 2fa code

When we delete an authorization, we often need to use basic
authentication because the client might not have the associated token
stored anymore. If 2fa is enabled, the client needs to be able to pass
that along.

Octokit/Http/IApiConnection.cs

@@ -203,6 +203,14 @@ namespace Octokit
         /// <returns>A <see cref="Task"/> for the request's execution.</returns>
         Task Delete(Uri uri);
 
+        /// <summary>
+        /// Deletes the API object at the specified URI.
+        /// </summary>
+        /// <param name="uri">URI of the API resource to delete</param>
+        /// <param name="twoFactorAuthenticationCode">Two Factor Code</param>
+        /// <returns>A <see cref="Task"/> for the request's execution.</returns>
+        Task Delete(Uri uri, string twoFactorAuthenticationCode);
+
         /// <summary>
         /// Deletes the API object at the specified URI.
         /// </summary>