tests: drivers: gpio: api_1pin: boards: update led0 on stm32n6570_dk

Replace the green user LED 1 with the red user LED 2 from alias led0
for the test to succeed.
LED1 is connect from a circuitry that prevents GPIO state from
triggering a interrupt while LED2 is directly wired to the GPIO pin.

While we're at it, change the LED's state from GPIO_ACTIVE_HIGH to
GPIO_ACTIVE_LOW to match the circuitry.

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