samples zbus benchmark: Fix twister filter

For the posix arch, this sample only works for native_posix,
all others will get a build error:
https://github.com/zephyrproject-rtos/zephyr/blob/main/samples/subsys/zbus/benchmark/src/benchmark.c#L20
So let's filter them.

Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>
1 file changed