Update user prompt for fetching GHSAs

Clarified the user prompt for fetching GitHub Security Advisories by specifying that the return_results option should be set to true.

Author: m-y-mo

src/seclab_taskflows/taskflows/audit/fetch_security_advisories.yaml

@@ -20,7 +20,7 @@ taskflow:
       model: general_tasks
       user_prompt: |
         Fetch and store all GitHub Security Advisories (GHSAs) for the repo {{ globals.repo }}
-        with the return_results option. 
+        with the return_results option set to true. 
 
         If an error occurs during fetching, store a GHSASummary with the error message.
         Ensure the error message starts with "Error:" followed by a description of the error.