Avoid redundant calls to `async_write_ha_state` in MQTT light (#100690)

homeassistant/components/mqtt/light/schema_basic.py

homeassistant/components/mqtt/light/schema_json.py

homeassistant/components/mqtt/light/schema_template.py

tests/components/mqtt/test_light.py

tests/components/mqtt/test_light_json.py

tests/components/mqtt/test_light_template.py