boards: stm32f072_eval: Remove outdated links

The STM32F072-EVAL board is now obsolete and the related documents are
no longer available on the official website.

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

Author: stephanosio

boards/arm/stm32f072_eval/doc/index.rst

@@ -40,8 +40,6 @@ Here are some highlights of the STM32F072-EVAL board:
      :align: center
      :alt: STM32F072-EVAL
 
-More information about the board can be found at the `STM32F072-EVAL website`_.
-
 Hardware
 ********
 
@@ -112,7 +110,7 @@ Pin Mapping
 STM32F072-EVAL Discovery kit has 6 GPIO controllers. These controllers are responsible for pin muxing,
 input/output, pull-up, etc.
 
-For mode details please refer to `STM32F072-EVAL board User Manual`_.
+For mode details please refer to STM32F072-EVAL board User Manual.
 
 Default Zephyr Peripheral Mapping:
 ----------------------------------
@@ -180,12 +178,6 @@ You can debug an application in the usual way.  Here is an example for the
    :goals: debug
 
 
-.. _STM32F072-EVAL website:
-   http://www.st.com/en/evaluation-tools/stm32072b-eval.html
-
-.. _STM32F072-EVAL board User Manual:
-   http://www.st.com/resource/en/user_manual/dm00104135.pdf
-
 .. _STM32F072VB on www.st.com:
    http://www.st.com/en/microcontrollers/stm32f072vb.html