tests: application_developement: ram_context_for_isr: exclude stm32n6570_dk

The test requires RAM-based vector table relocation
(CONFIG_SRAM_VECTOR_TABLE), which depends on CONFIG_XIP being enabled.
However, stm32n6570_dk lacks internal flash and does not support XIP,
making SRAM vector relocation unsupported.As a result, the test cannot
validate ISR execution from RAM on this platform.

Signed-off-by: Fabrice DJIATSA <fabrice.djiatsa-ext@st.com>