[cert] capitalize python class constants (#5080)

According to PEP8, constants should be written in all capital letters.

This commit capitalizes these constants:
- thread_cert.TestCase.topology
- thread_cert.TestCase.support_ncp

tests/scripts/thread-cert/test_route_table.py

@@ -41,7 +41,7 @@ ROUTER2 = 3
 
 
 class TestRouteTable(thread_cert.TestCase):
-    topology = {
+    TOPOLOGY = {
         LEADER: {
             'mode': 'rsdn',
             'panid': 0xface,