Fix example on comparing master config (#32406)

Current example produces error message: 

"msg": "Unsupported parameters for (ios_config) module: diff_config Supported parameters include: after,auth_pass,authorize,backup,before,defaults,diff_against,diff_ignore_lines,force,host,intended_config,lines,match,multiline_delimiter,parents,password,port,provider,replace,running_config,save,save_when,src,ssh_keyfile,timeout,username"

lib/ansible/modules/network/ios/ios_config.py

@@ -248,7 +248,7 @@ EXAMPLES = """
 
 - name: check the running-config against master config
   ios_config:
-    diff_config: intended
+    diff_against: intended
     intended_config: "{{ lookup('file', 'master.cfg') }}"
 
 - name: check the startup-config against the running-config