Samples: zbus: benchmark: Exclude nrf52_bsim

For the POSIX arch, this test relays on the native_posix RTC.
But that does not exist in the nrf52_bsim.
And without something to measure actual execution time,
it does not make sense to benchmark in the POSIX arch.
So disable this test for this platform,
and add a clear build error to warn users.

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