Remove check for API version in validate_scheduling

API version 1.37 is from Queens, we can safelly remove
the verification for resource class and traits, since
the releases older than queens are not supported.

Change-Id: Ie84504670c8ac017324f903bb5ac45e1e837f5ac
diff --git a/ironic_tempest_plugin/tests/scenario/test_baremetal_basic_ops.py b/ironic_tempest_plugin/tests/scenario/test_baremetal_basic_ops.py
index 7912788..0cfbff0 100644
--- a/ironic_tempest_plugin/tests/scenario/test_baremetal_basic_ops.py
+++ b/ironic_tempest_plugin/tests/scenario/test_baremetal_basic_ops.py
@@ -151,21 +151,8 @@
         those set on the node. Does not assume that resource classes and traits
         are in use.
         """
-        # Try to get a node with resource class (1.21) and traits (1.37).
-        # TODO(mgoddard): Remove this when all stable releases support these
-        # API versions.
-        for version in ('1.37', '1.21'):
-            if self._is_version_supported(version):
-                node = self.get_node(instance_id=self.instance['id'],
-                                     api_version=version)
-                break
-        else:
-            # Neither API is supported - cannot test.
-            LOG.warning("Cannot validate resource class and trait based "
-                        "scheduling as these require API version 1.21 and "
-                        "1.37 respectively")
-            return
-
+        node = self.get_node(instance_id=self.instance['id'],
+                             api_version='1.37')
         f_id = self.instance['flavor']['id']
         extra_specs = self.flavors_client.list_flavor_extra_specs(f_id)
         extra_specs = extra_specs['extra_specs']