i915/gem_exec_schedule: Only require the scheduler

If the legacy ringbuffer doesn't support scheduling, it doesn't set the
cap! Hypothetically if one were to enable ringbuffer scheduling, this is
part of its testing suite.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

tests/i915/gem_exec_schedule.c

@@ -1774,9 +1774,6 @@ igt_main
 		igt_fixture {
 			igt_require(gem_scheduler_enabled(fd));
 			igt_require(gem_scheduler_has_ctx_priority(fd));
-
-			/* need separate rings */
-			igt_require(gem_has_execlists(fd));
 		}
 
 		for (e = intel_execution_engines; e->name; e++) {