tests: drivers.gpio.1pin: re-enable hifive1

This commit removes the `hifive1` board from the `platform_exclude` list
for the `drivers.gpio.1pin` pin.

The root cause for why this platform was disabled was fixed in the recent
Renode version upgrade in the CI image.

Fixes #69350.

Signed-off-by: Filip Kokosinski <fkokosinski@antmicro.com>