update user manual

Author: Hannes7eicher

content/hardware/03.nano/boards/nano-matter/tutorials/01.user-manual/content.md

@@ -36,11 +36,7 @@ This user manual will guide you through a practical journey covering the most in
 
 ### Board Core and Libraries
 
-The **Silicon Labs** core contains the libraries and examples you need to work with the board's components, such as its Matter, Bluetooth® Low Energy, and I/Os. To install the Nano Matter core, navigate to **File > Preferences** and in the **Additional boards manager URLs**, add the following:
-
-`https://siliconlabs.github.io/arduino/package_arduinosilabs_index.json`
-
-Now navigate to **Tools > Board > Boards Manager** or click the Boards Manager icon in the left tab of the IDE. In the Boards Manager tab, search for `Nano Matter` and install the latest `Silicon Labs` core version.
+The **Silicon Labs** core contains the libraries and examples you need to work with the board's components, such as its Matter, Bluetooth® Low Energy, and I/Os. To install the Nano Matter core, navigate to **Tools > Board > Boards Manager** or click the Boards Manager icon in the left tab of the IDE. In the Boards Manager tab, search for `Nano Matter` and install the latest `Silicon Labs` core version.
 
 ![Installing the Silicon Labs core in the Arduino IDE](assets/bsp-install-2.png)