Fix class name for test extensions

Remove json from class name

Change-Id: Ie165e1309136913d3a7ca801056e081f09de2e27
diff --git a/tempest/api/compute/test_extensions.py b/tempest/api/compute/test_extensions.py
index 42e13bd..ef5a38f 100644
--- a/tempest/api/compute/test_extensions.py
+++ b/tempest/api/compute/test_extensions.py
@@ -26,7 +26,7 @@
 LOG = logging.getLogger(__name__)
 
 
-class ExtensionsTestJSON(base.BaseV2ComputeTest):
+class ExtensionsTest(base.BaseV2ComputeTest):
 
     @decorators.idempotent_id('3bb27738-b759-4e0d-a5fa-37d7a6df07d1')
     def test_list_extensions(self):