schedule_api: don't exclude Nios II

Nothing about this test requires tickless idle and it's not even
turned on in prj.conf.

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
diff --git a/tests/kernel/threads_scheduling/schedule_api/testcase.ini b/tests/kernel/threads_scheduling/schedule_api/testcase.ini
index effdb40..58c4d1a 100644
--- a/tests/kernel/threads_scheduling/schedule_api/testcase.ini
+++ b/tests/kernel/threads_scheduling/schedule_api/testcase.ini
@@ -1,4 +1,2 @@
 [test]
 tags = kernel
-# tickless is not supported on nios2
-arch_exclude = nios2