tests: ram_context_for_isr: exclude STM32C0 boards

The test attempts to register an ISR for an IRQ
used by a device driver on this platform.
This breaks builds of the test and makes CI red.

Temporarily exclude all C0-based platforms from
the test until a clean solution is implemented.

Signed-off-by: Mathieu CHOPLAIN <mathieu.choplain@st.com>