readme: remove doc from list of features

Documentation is not (yet) provided.

Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>

Author: gmarull

README.md

@@ -8,7 +8,6 @@ applications. Some of the features demonstrated in this example are:
 - [Custom boards][board_porting]
 - Custom [devicetree bindings][bindings]
 - Out-of-tree [drivers][drivers]
-- Documentation using Doxygen and Sphinx
 - Example CI configuration (using Github Actions)
 
 [board_porting]: https://docs.zephyrproject.org/latest/guides/porting/board_porting.html