Convert draft Hardening Guide to asciidoc

Removed admonition

Complete asciidoc conversion of v3 Hardening Guide

https://issues.redhat.com/browse/AAP-43908

Author: ianf77

downstream/modules/aap-hardening/con-credential-management-planning.adoc

@@ -9,12 +9,6 @@
 
 {PlatformName} uses credentials to authenticate requests to jobs against machines, synchronize with inventory sources, and import project content from a version control system. 
 
-[IMPORTANT]
-====
-In the context of {ControllerName} and {EDAcontroller}, you can use both `extra_vars` and credentials to store a variety of information. 
-However, credentials are the preferred method of storing sensitive information such as passwords or API keys because they offer better security and centralized management, whereas `extra_vars` are more suitable for passing dynamic, non-sensitive data.
-====
-
 {ControllerNameStart} manages three sets of secrets:
 
 * User passwords for *local {PlatformNameShort} users*.