use new module name in example

Author: roycaihw

examples/pod_exec.py

@@ -20,7 +20,7 @@
 
 from kubernetes import config
 from kubernetes.client import Configuration
-from kubernetes.client.apis import core_v1_api
+from kubernetes.client.api import core_v1_api
 from kubernetes.client.rest import ApiException
 from kubernetes.stream import stream