k8s_auth: use group module defaults in example (#52712)

The yaml anchor thing was just a stopgap until all the module defaults
group stuff got merged. Which it did.

lib/ansible/modules/clustering/k8s/k8s_auth.py

@@ -74,42 +74,37 @@ requirements:
 '''
 
 EXAMPLES = '''
-- block:
+- hosts: localhost
+  module_defaults:
+    group/k8s:
+      host: https://k8s.example.com/
+      ssl_ca_cert: ca.pem
+  tasks:
+  - block:
     # It's good practice to store login credentials in a secure vault and not
     # directly in playbooks.
     - include_vars: k8s_passwords.yml
 
     - name: Log in (obtain access token)
       k8s_auth:
-      host: https://k8s.example.com/
-      ssl_ca_cert: ca.pem
         username: admin
         password: "{{ k8s_admin_password }}"
       register: k8s_auth_results
 
-  - name: Preserve auth info as both a fact and a yaml anchor for easy access later
-    # Both the fact and the anchor are called 'k8s_auth_params'
-    set_fact:
-      k8s_auth_params: &k8s_auth_params
-        host: "{{ k8s_auth_results.k8s_auth.host }}"
-        ssl_ca_cert: "{{ k8s_auth_results.k8s_auth.ssl_ca_cert }}"
-        verify_ssl: "{{ k8s_auth_results.k8s_auth.verify_ssl }}"
-        api_key: "{{ k8s_auth_results.k8s_auth.api_key }}"
-
-  # Previous task generated I(k8s_auth) fact, which you can then use
-  # in k8s modules like this:
+    # Previous task provides the token/api_key, while all other parameters
+    # are taken from module_defaults
     - name: Get a list of all pods from any namespace
       k8s_facts:
-      <<: *k8s_auth_params
+        api_key: "{{ k8s_auth_results.k8s_auth.api_key }}"
         kind: Pod
       register: pod_list
 
     always:
     - name: If login succeeded, try to log out (revoke access token)
-    when: k8s_auth_params is defined
+      when: k8s_auth_results.k8s_auth.api_key is defined
       k8s_auth:
         state: absent
-      <<: *k8s_auth_params
+        api_key: "{{ k8s_auth_results.k8s_auth.api_key }}"
 '''
 
 # Returned value names need to match k8s modules parameter names, to make it