tests: arch: arm_irq_vector_table: exclude mr_canhubk3 board

The mr_canhubk3 board enables by default an off-chip watchdog that must
be serviced to avoid triggering a reset and cannot be disabled on a
per-test basis.

To add the needed ISR for this test involve doing modifications to the
LPSPI MCUX driver that does not worth the trouble for this test only,
so exclude this board.

Signed-off-by: Manuel Argüelles <manuel.arguelles@nxp.com>