samples/*/*shell: filter test with shell harness on bsim targets

The shell harness expects the UART can be routed to stdin/out on POSIX
arch based targets, but this is not the case for the bsim targets (at
least not yet, and not using the native_posix UART configuration option)

This causes these tests to fail timing out in CI => let's filter these
platforms by now.

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