Revert "thermostat: show temperature in red if heater is on"

This reverts commit 21b3521326.

QPushButtons don't handle rich text format

soft/thermostat/src/zoneitem.cpp

@@ -47,15 +47,10 @@ void ZoneItem::refresh(void)
 {
 	QString text;
 
-	if ((m_temperature_value == FORCE_OFF) || !m_available) {
+	if ((m_temperature_value == FORCE_OFF) || !m_available)
 		text += QString("-");
-	} else {
-		if (m_heating_on)
-			text.append(QString("<font color=red>"));
+	else
 		text += QString::number(m_temperature_value);
-		if (m_heating_on)
-			text.append(QString("</font>"));
-	}
 	text += QString("°C / ");
 
 	if (m_target_temperature == FORCE_OFF) {