doc: Fix warning associated with GNU ARM embedded rename
doc: Fix warning associated with GNU ARM embedded rename

We missed one reference to GCC ARM Embedded when we renamed it to GNU
ARM Embedded.

Signed-off-by: Kumar Gala <a5e5248af4cd4f0ed8c515f61d40a6e2db46a66e@linaro.org>

galak/zephyr,ldts/zephyr,kraj/zephyr,ldts/zephyr,Vudentz/zephyr,kraj/zephyr,Vudentz/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,kraj/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,Vudentz/zephyr,explora26/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,explora26/zephyr,explora26/zephyr,finikorg/zephyr,galak/zephyr,punitvara/zephyr,nashif/zephyr,finikorg/zephyr,Vudentz/zephyr,galak/zephyr,punitvara/zephyr,Vudentz/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,punitvara/zephyr,nashif/zephyr,finikorg/zephyr,kraj/zephyr,nashif/zephyr,ldts/zephyr,ldts/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,punitvara/zephyr,Vudentz/zephyr,explora26/zephyr,punitvara/zephyr,kraj/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr