Remove stale MQTT JSON processing documentation (#13836)

source/_docs/mqtt.markdown

@@ -23,6 +23,5 @@ For detailed setup instructions, please refer to the [MQTT broker](/docs/mqtt/br
 - [Birth and last will messages](/docs/mqtt/birth_will/)
 - [Testing your setup](/docs/mqtt/testing/)
 - [Logging](/docs/mqtt/logging/)
-- [Processing JSON](/docs/mqtt/processing_json/)
 
 See the [MQTT example component](/cookbook/python_component_mqtt_basic/) how to integrate your own component.

source/_docs/mqtt/processing_json.markdown

@@ -1,30 +0,0 @@
----
-title: "Processing JSON"
-description: "Instructions on how to process the MQTT payload."
-logo: mqtt.png
----
-
-The MQTT [switch](/integrations/switch.mqtt/) and [sensor](/integrations/sensor.mqtt/) platforms support processing JSON over MQTT messages and parsing them using JSONPath. JSONPath allows you to specify where in the JSON the value resides that you want to use. The following examples will always return the value `100`.
-
-| JSONPath query | JSON |
-| -------------- | ---- |
-| `somekey` | `{ 'somekey': 100 }`
-| `somekey[0]` | `{ 'somekey': [100] }`
-| `somekey[0].value` | `{ 'somekey': [ { value: 100 } ] }`
-
-To use this, add the following key to your `configuration.yaml`:
-
-```yaml
-switch:
-  platform: mqtt
-  state_format: 'json:somekey[0].value'
-```
-It is also possible to extract JSON values by using a value template:
-
-```yaml
-switch:
-  platform: mqtt
-  value_template: '{% raw %}{{ value_json.somekey[0].value }}{% endraw %}'
-```
-
-More information about the full JSONPath syntax can be found [in their documentation](https://github.com/kennknowles/python-jsonpath-rw#jsonpath-syntax).

source/_integrations/mqtt.markdown

@@ -51,4 +51,3 @@ This allows you to connect to the MQTT broker with user `homeassistant` and pass
 - [Birth and last will messages](/docs/mqtt/birth_will/)
 - [Testing your setup](/docs/mqtt/testing/)
 - [Logging](/docs/mqtt/logging/)
-- [Processing JSON](/docs/mqtt/processing_json/)