Fixed indent of `refresh` in `external_components`

Thanks to @maartenpaul for the heads up!

example.yaml

@@ -115,7 +115,7 @@ external_components:
       type: git
       url: https://github.com/mmakaay/esphome-xiaomi_bslamp2
       ref: main
-      refresh: 60s
+    refresh: 60s
 
 # A special platform package is used for enabling unicore and disabling the
 # efuse mac crc check. These two changes are required for the ESP32-WROOM-32D