boards: electronut: adopt new zephyr:board directive and role

This updates the documentation of all the Electronut boards to use
the new `zephyr:board::` directive.

Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>

boards/electronut/nrf52840_blip/doc/index.rst

@@ -1,7 +1,4 @@
-.. _nrf52840_blip:
-
-Electronut Labs Blip
-####################
+.. zephyr:board:: nrf52840_blip
 
 Overview
 ********
@@ -25,12 +22,6 @@ nRF52840 ARM Cortex-M4F CPU and the following devices:
 * :abbr:`USB (Universal Serial Bus)`
 * :abbr:`WDT (Watchdog Timer)`
 
-.. figure:: img/nrf52840_blip.jpg
-     :align: center
-     :alt: Electronut Labs Blip
-
-     Electronut Labs Blip (Credit: Electronut Labs)
-
 More information about the board is available at https://github.com/electronut/ElectronutLabs-blip.
 
 Hardware

boards/electronut/nrf52840_papyr/doc/nrf52840_papyr.rst

@@ -1,7 +1,4 @@
-.. _nrf52840_papyr:
-
-Electronut Labs Papyr
-#####################
+.. zephyr:board:: nrf52840_papyr
 
 Overview
 ********
@@ -27,12 +24,6 @@ the following devices:
 * :abbr:`WDT (Watchdog Timer)`
 * COUNTER
 
-.. figure:: img/nrf52840_papyr.jpg
-     :align: center
-     :alt: Electronut Labs Papyr
-
-     Electronut Labs Papyr (Credit: Electronut Labs)
-
 More information about the board is available at https://gitlab.com/electronutlabs-public/papyr.
 
 Hardware