MAINTAINERS: Remove myself as SiLabs collaborator
MAINTAINERS: Remove myself as SiLabs collaborator

I am not using Silicon Labs platform for a while now and will not be for
the foreseeable future.

Signed-off-by: Christian Taedcke <5dfb12f5b8690cb9c18e955016e7e3173b81d0d8@lemonbeat.com>

zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,galak/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr