Fix dead Zephyr board doc link for B-L475E-IOT01A (#821) (#824)

Zephyr reorganized its board documentation from boards/<arch>/ to
boards/<vendor>/, so the boards/arm/disco_l475_iot1 link 404s. Point
it at the current boards/st/disco_l475_iot1 path.



(cherry picked from commit f14ade1)

Signed-off-by: ismetvahidzade986-sketch <277601556+ismetvahidzade986-sketch@users.noreply.github.com>
Co-authored-by: Ismet Vahidezade <ismetvahidzade986@gmail.com>
Co-authored-by: ismetvahidzade986-sketch <277601556+ismetvahidzade986-sketch@users.noreply.github.com>

Author: mergify[bot]

README.md

@@ -39,7 +39,7 @@ This package provides tools and utils to crosscompile micro-ROS with just the co
 | [FreeRTOS](https://www.freertos.org/)                                                                               | [Crazyflie 2.1](https://www.bitcraze.io/crazyflie-2-1/)                                                                                                                                  | v10.2.1 - CF 2020.06         | `freertos crazyflie21`       |                                                                                                                                        |
 | [Zephyr](https://www.zephyrproject.org/)                                                                            | [Olimex STM32-E407](https://www.olimex.com/Products/ARM/ST/STM32-E407/open-source-hardware)                                                                                              | v2.6.0                       | `zephyr olimex-stm32-e407`   | **[micro-ROS module for Zephyr RTOS](https://github.com/micro-ROS/micro_ros_zephyr_module)**                                           |
 | [Zephyr](https://www.zephyrproject.org/)                                                                            | [ST Nucleo F446RE](https://www.st.com/en/evaluation-tools/nucleo-f446re.html)  <sup>1</sup>                                                                                              | v2.6.0                       | `zephyr nucleo_f446re`       | **[micro-ROS module for Zephyr RTOS](https://github.com/micro-ROS/micro_ros_zephyr_module)**                                           |
-| [Zephyr](https://www.zephyrproject.org/)                                                                            | [ST B-L475E-IOT01A](https://docs.zephyrproject.org/latest/boards/arm/disco_l475_iot1/doc/index.html)                                                                                     | v2.6.0                       | `zephyr discovery_l475_iot1` | **[micro-ROS module for Zephyr RTOS](https://github.com/micro-ROS/micro_ros_zephyr_module)**                                           |
+| [Zephyr](https://www.zephyrproject.org/)                                                                            | [ST B-L475E-IOT01A](https://docs.zephyrproject.org/latest/boards/st/disco_l475_iot1/doc/index.html)                                                                                      | v2.6.0                       | `zephyr discovery_l475_iot1` | **[micro-ROS module for Zephyr RTOS](https://github.com/micro-ROS/micro_ros_zephyr_module)**                                           |
 | [Zephyr](https://www.zephyrproject.org/)                                                                            | [ST Nucleo H743ZI](https://www.st.com/en/evaluation-tools/nucleo-h743zi.html) <sup>1</sup>                                                                                               | v2.6.0                       | `zephyr nucleo_h743zi`       | **[micro-ROS module for Zephyr RTOS](https://github.com/micro-ROS/micro_ros_zephyr_module)**                                           |
 | [Zephyr](https://www.zephyrproject.org/)                                                                            | [Zephyr emulator](https://docs.zephyrproject.org/2.3.0/boards/posix/native_posix/doc/index.html)                                                                                         | v2.6.0                       | `zephyr host`                | **[micro-ROS module for Zephyr RTOS](https://github.com/micro-ROS/micro_ros_zephyr_module)**                                           |
 | [Mbed](https://os.mbed.com/)                                                                                        | [ST B-L475E-IOT01A](https://os.mbed.com/platforms/ST-Discovery-L475E-IOT01A/)                                                                                                            | v6.6                         | `mbed disco_l475vg_iot01a`   | **[micro-ROS module for Mbed RTOS](https://github.com/micro-ROS/micro_ros_mbed)**                                                      |