doc: remove reference to deleted sample code
doc: remove reference to deleted sample code

A legacy sample was remove, so delete reference to it.

Change-Id: Ibd2d5fd25d799974bf60fe18847262ecbc0d3ea4
Signed-off-by: David B. Kinder <c56c8b29908a5b2af1b63001268d73a0b7f972ba@intel.com>

tidyjiang8/zephyr-doc,tidyjiang8/zephyr-doc,tidyjiang8/zephyr-doc,tidyjiang8/zephyr-doc,tidyjiang8/zephyr-doc