[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_Cli.py

@@ -35,7 +35,7 @@ LEADER = 1
 
 
 class Cert_Cli(thread_cert.TestCase):
-    topology = {
+    TOPOLOGY = {
         LEADER: {},
     }