Update 07_multi_container.md (#23010)

Update blog post URL.

## Description
The blog post link detailing why using env vars in production is
discouraged, is broken.
Updated link to blog post to post's new location.

Author: gumacahin

content/get-started/workshop/07_multi_container.md

@@ -192,7 +192,7 @@ The todo app supports the setting of a few environment variables to specify MySQ
 >
 > While using env vars to set connection settings is generally accepted for development, it's highly discouraged
 > when running applications in production. Diogo Monica, a former lead of security at Docker,
-> [wrote a fantastic blog post](https://diogomonica.com/2017/03/27/why-you-shouldnt-use-env-variables-for-secret-data/)
+> [wrote a fantastic blog post](https://blog.diogomonica.com/2017/03/27/why-you-shouldnt-use-env-variables-for-secret-data/)
 > explaining why.
 >
 > A more secure mechanism is to use the secret support provided by your container orchestration framework. In most cases,