Update additional reading list in 5-summary.md

Removed 'DevOps for Dummies' from additional reading list.

Author: Albertyang0

learn-pr/advocates/improve-reliability-introduction/includes/5-summary.md

@@ -8,5 +8,4 @@ Improving your reliability can definitely be a challenge, but it's a necessary c
 ## Additional Reading
 
 - [What is DevOps?](/azure/devops/learn/what-is-devops)
-- [DevOps for Dummies](https://www.dummies.com/)
-- [Azure SRE hub](/azure/site-reliability-engineering/)
+- [Azure SRE hub](/azure/site-reliability-engineering/)