Fix callout build error from escaped shortcode syntax

[simihablo]

Summary

• Fix Hugo build error in the content-formatting-examples page where escaped shortcode delimiters ({{</* */>}}) inside a hextra/callout body caused markdownify to fail with "shortcode has no name"
• Hugo resolves escaped shortcode syntax to literal delimiters in .InnerDeindent, which then breaks markdownify processing
• Reworded the callout text to describe the delimiter syntax without using literal shortcode notation

Test plan

• Verify the Hugo build completes without errors: hugo --gc --minify -D
• Verify the content-formatting-examples page renders the Hextra callout correctly
• Confirm no other shortcode examples are affected

[Copilot]

Pull request overview

This PR updates the content-formatting-examples documentation to avoid a Hugo build failure caused by escaped shortcode delimiters being included inside a hextra/callout body that is processed via markdownify.

Changes:

• Reworded the informational hextra/callout text to describe shortcode delimiter usage without including literal escaped shortcode syntax that can break markdownify.

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