Merge branch 'bugfix/mqtt_docs_migration_5.x' into 'master'

mqtt/docs: Mention removal of user_context in 5.x migration guide

Closes IDFGH-9261

See merge request espressif/esp-idf!22177

docs/en/migration-guides/release-5.x/5.0/protocols.rst

@@ -169,7 +169,7 @@ MQTT Client
 Breaking Changes (Summary)
 ~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-- :cpp:type:`esp_mqtt_client_config_t` have all fields grouped in sub structs. 
+- :cpp:type:`esp_mqtt_client_config_t` have all fields grouped in sub structs.
 
 Most common configurations are listed below:
 
@@ -177,9 +177,11 @@ Most common configurations are listed below:
 - Security related to broker verification in :cpp:member:`esp_mqtt_client_config_t::broker::verification`
 - Client username is set in :cpp:member:`esp_mqtt_client_config_t::credentials::username`
 
+- :cpp:type:`esp_mqtt_client_config_t` no longer supports the ``user_context`` field. Please use :cpp:func:`esp_mqtt_client_register_event` instead for registering an event handler; the last argument ``event_handler_arg`` can be used to pass user context to the handler.
+
 
 ESP-Modbus
-----------
+-----------
 
 Breaking Changes (Summary)
 ~~~~~~~~~~~~~~~~~~~~~~~~~~

docs/zh_CN/migration-guides/release-5.x/5.0/protocols.rst

@@ -177,6 +177,8 @@ MQTT 客户端
 - 通过 :cpp:member:`esp_mqtt_client_config_t::broker::verification` 配置 MQTT Broker 身份验证的相关安全问题
 - 通过 :cpp:member:`esp_mqtt_client_config_t::credentials::username` 配置客户端用户名
 
+- :cpp:type:`esp_mqtt_client_config_t` 不再支持 ``user_context`` 字段。之后注册事件处理程序，请使用 :cpp:func:`esp_mqtt_client_register_event`；最后一个参数 ``event_handler_arg`` 可用于将用户上下文传递给处理程序。
+
 
 ESP-Modbus
 ----------