Remove unrelated esp32 stanza from example code (#5472)

This page describes the 'esphome' section so doesn't need to include
the esp32 section which itself includes the old 'board' line rather than
the preferred 'variant' setting

Co-authored-by: Jonathan Swoboda <[email protected]>

Author: Elwell

content/components/esphome.md

@@ -17,9 +17,6 @@ esphome:
     name: livingroom
     comment: Living room ESP32 controller
     area: Living Room
-
-esp32:
-    board: nodemcu-32s
 ```
 
 {{< anchor "esphome-configuration_variables" >}}