tests: arm_irq_vector_table: Disable bellboard for nRF54/nRF92

This test uses the bellboard interrupts for the application
and the radio core builds on nRF54H20 and nRF9280.
Since it uses the bellboard interrupts it makes sense to ensure
that bellboard is disabled in device tree to avoid runtime issues.

This is preparation work, bellboard is planned to be enabled
by default later and this makes sure that the test will
continue to work.

Signed-off-by: Georgios Vasilakis <georgios.vasilakis@nordicsemi.no>