typo in code example. (home-assistant#3422)

ericmharris · fabaff · commit 707343c68ea1 · 2017-09-23T17:40:16.000+02:00
diff --git a/source/_components/sensor.wunderground.markdown b/source/_components/sensor.wunderground.markdown
@@ -158,7 +158,7 @@ group:
 ```yaml
 sensor:
   - platform: wunderground
-  - api_key: your_api_key
+    api_key: your_api_key
     monitored_conditions:
       - temp_high_record_c
       - temp_high_1d_c
