boards: blackpill: Fix incorrect hyperlink references

This commit fixes incorrect external hyperlink references in the
Blackpill board documentation.

Signed-off-by: Stephanos Ioannidis <[email protected]>

Author: stephanosio

boards/arm/blackpill_f401cc/doc/index.rst

@@ -10,7 +10,7 @@ The WeAct Black Pill V1.2 Board is an extremely low cost and bare-bones
 development board featuring the STM32F401CC, see `STM32F401CC website`_.
 This is the 48-pin variant of the STM32F401x series,
 see `STM32F401x reference manual`_. More info about the board available
-`here <stm32-base-board-page>`_ and on `WeAct Github`_.
+`here <stm32-base-board-page_>`_ and on `WeAct Github`_.
 
 .. image:: img/blackpill-v3.jpg
       :align: center

boards/arm/blackpill_f401ce/doc/index.rst

@@ -10,7 +10,7 @@ The WeAct Black Pill V3.0 Board is an extremely low cost and bare-bones
 development board featuring the STM32F401CE, see `STM32F401CE website`_.
 This is the 48-pin variant of the STM32F401x series,
 see `STM32F401x reference manual`_. More info about the board available
-`here <stm32-base-board-page>`_ and on `WeAct Github`_.
+`here <stm32-base-board-page_>`_ and on `WeAct Github`_.
 
 .. image:: img/blackpill-v3.jpg
       :align: center

boards/arm/blackpill_f411ce/doc/index.rst

@@ -10,7 +10,7 @@ The WeAct Black Pill V2.0 Board is an extremely low cost and bare-bones
 development board featuring the STM32F411CE, see `STM32F411CE website`_.
 This is the 48-pin variant of the STM32F411x series,
 see `STM32F411x reference manual`_. More info about the board available
-`here <stm32-base-board-page>`_ and on `WeAct Github`_.
+`here <stm32-base-board-page_>`_ and on `WeAct Github`_.
 
 .. image:: img/blackpill-v2.jpg
       :align: center

boards/arm/stm32f401_mini/doc/index.rst

@@ -8,7 +8,7 @@ Overview
 
 The STM32 Mini F401 is an extremely low cost and bare-bones
 development board featuring the STM32F401CC, see `STM32F401CC website`_.
-More info about the board with schematics available `here <stm32-base-board-page>`_
+More info about the board with schematics available `here <stm32-base-board-page_>`_
 
 .. image:: img/STM32_Mini_F401-1.jpg
       :align: center