Use note callout for security reminder (#2491)

Author: Copilot

workshop/side-quest-17-02-security-architecture.md

@@ -69,7 +69,7 @@ Good output usually:
 - Avoids secrets, tokens, credentials, and private personal data.
 - Stays within the permissions and intent you defined.
 
-> [!IMPORTANT]
+> [!NOTE]
 > Treat logs and comments as public-to-collaborators surfaces. Never design prompts that ask the agent to print secrets.
 
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