Temperature usermod: fix changelog formatting

This change ensures that the dates are displayed on their own lines.
Without the blank lines, many Markdown renderers will append the dates
to the previous bullet point.

usermods/Temperature/readme.md

@@ -56,8 +56,10 @@ lib_deps =
 * Do not report erroneous low temperatures to MQTT
 * Disable plugin if temperature sensor not detected
 * Report the number of seconds until the first read in the info screen instead of sensor error
+
 2021-04
 * Adaptation for runtime configuration.
+
 2023-05
 * Rewrite to conform to newer recommendations.
 * Recommended @blazoncek fork of OneWire for ESP32 to avoid Sensor error