fix: disable special handlers for impersonate grant type

Author: ksavosteev

src/VirtoCommerce.Platform.Web/Controllers/Api/AuthorizationController.cs

@@ -335,8 +335,6 @@ public async Task<ActionResult> Exchange()
                     }
                 }
 
-                await HandleTokenRequest(impersonatedUser, context); //?????
-
                 // Create a new authentication ticket, but reuse the properties stored in the
                 // authorization code/refresh token, including the scopes originally granted.
                 var ticket = await CreateTicketAsync(impersonatedUser, context);