Define and use TCX5 waiver for AsciiDoc

cr: https://code.amazon.com/reviews/CR-224676594

Author: stephswo

v2/guide/best-practices-security.adoc

@@ -6,6 +6,7 @@ include::attributes.txt[]
 [[best-practices-security,best-practices-security.title]]
 = {aws} CDK security best practices
 :info_titleabbrev: Security
+:tcx5-2025-waiver: 		 	 	 
 :keywords: {aws} CDK, IAM, security, permissions, infrastructure, {aws} CloudFormation, {aws} CDK deployments
 
 [abstract]
@@ -52,7 +53,7 @@ To configure the IAM identities in your {aws} account with permission to assume
 [source,json,subs="verbatim,attributes"]
 ----
 {
-  "Version": "2012-10-17",&TCX5-2025-waiver;
+  "Version": "2012-10-17",{tcx5-2025-waiver}
   "Statement": [{
     "Sid": "AssumeCDKRoles",
     "Effect": "Allow",