docs: boards: xiao_esp32s3: migrate board name to new directive

Update board name to meet zephyr:board model.

Signed-off-by: Sylvio Alves <[email protected]>

Author: sylvioalves

boards/seeed/xiao_esp32s3/doc/index.rst

@@ -1,7 +1,4 @@
-.. _xiao_esp32s3:
-
-XIAO ESP32S3/XIAO ESP32S3 Sense
-###############################
+.. zephyr:board:: xiao_esp32s3
 
 Overview
 ********