test: drivers: gpio: gpio_basic_api: disable interrupt at end of test

When switching from rising edge to falling edge of test:
test_gpio_deprecated(),
because exti callback is already configured (from rising edge test),
the pin configuration abort for EBUSY reason.
It is necessary to disable interrupt,
so that next test will start with clean configuration.

Signed-off-by: Alexandre Bourdiol <alexandre.bourdiol@st.com>