docs: fix typo

Author: kenjis

user_guide_src/source/installation/upgrade_responses.rst

@@ -17,7 +17,7 @@ What has been changed
 
 Upgrade Guide
 =============
-1. The methods in the HTTP Responses class are named slightly different. The most important change in the naming is the switch from underscored method names to camelCase. The method ``set_content_type()`` from version 3 is now named ``setContentType()`` and so on.
+1. The methods in the HTTP Response class are named slightly different. The most important change in the naming is the switch from underscored method names to camelCase. The method ``set_content_type()`` from version 3 is now named ``setContentType()`` and so on.
 2. In the most cases you have to change ``$this->output`` to ``$this->response`` followed by the method. You can find all methods in :doc:`../outgoing/response`.
 
 Code Example