support/testing/tests/init/init_openrc: fix flake8 F401 warning

Fixes:

support/testing/tests/init/test_openrc.py:1:1: F401 'infra.basetest' imported but unused

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

support/testing/tests/init/test_openrc.py

@@ -1,4 +1,3 @@
-import infra.basetest
 from tests.init.base import InitSystemBase as InitSystemBase