Update note about Firewall for AI content-type

Clarified that Firewall for AI only triggers on 'content-type' json.

Author: DavidJKTofan

src/content/docs/waf/detections/firewall-for-ai.mdx

@@ -42,6 +42,7 @@ Firewall for AI is available in closed beta to Enterprise customers proxying tra
 
 :::note
 Firewall for AI is only available in the new [application security dashboard](/security/).
+Additionally, it only triggers on `content-type` json.
 :::
 
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