Do not enable SHT3x heater by default. Fixes esphome#4886.

The SHT sensor heater is for special use and defaulting
them to on breaks the vast majority of prior configs and
seems quite surprising. This appears to have been an
inadvertent side effect of PR esphome#5161.

esphome/components/sht3xd/sensor.py

@@ -38,7 +38,7 @@
                 device_class=DEVICE_CLASS_HUMIDITY,
                 state_class=STATE_CLASS_MEASUREMENT,
             ),
-            cv.Optional(CONF_HEATER_ENABLED, default=True): cv.boolean,
+            cv.Optional(CONF_HEATER_ENABLED, default=False): cv.boolean,
         },
     )
     .extend(cv.polling_component_schema("60s"))