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

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

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

boards/lilygo/ttgo_lora32/doc/index.rst

@@ -1,7 +1,4 @@
-.. _ttgo_lora32:
-
-Lilygo TTGO LoRa32
-##################
+.. zephyr:board:: ttgo_lora32
 
 Overview
 ********
@@ -18,13 +15,6 @@ It's available in two versions supporting two different frequency ranges and fea
 
 Some of the ESP32 I/O pins are accessible on the board's pin headers.
 
-.. figure:: img/ttgo_lora32.webp
-        :align: center
-        :alt: Lilygo TTGO LoRa32 module
-        :width: 400 px
-
-        Lilygo TTGO LoRa32 module
-
 Functional Description
 **********************
 

boards/lilygo/ttgo_t8c3/doc/index.rst

@@ -1,7 +1,4 @@
-.. _ttgo_t8c3:
-
-Lilygo TTGO T8-C3
-#################
+.. zephyr:board:: ttgo_t8c3
 
 Overview
 ********
@@ -17,12 +14,6 @@ It features the following integrated components:
 - JST GH 2-pin battery connector
 - LED
 
-.. figure:: img/ttgo_t8c3.webp
-   :align: center
-   :alt: TTGO T8-C3
-
-   Lilygo TTGO T8-C3
-
 Functional Description
 **********************
 This board is based on the ESP32-C3 with 4MB of flash, WiFi and BLE support. It