Disable DAST profile selection only for selected profile

Related issue - #364444 (closed)

What does this MR do and why?

This fixes an issue where DAST profile selection was disabled for "in use" profiles. This is now fixed by disabling the profile selection only when the profile is currently selected.

More details are in #364444 (closed)

Screenshots or screen recordings

dast_select_btn_fix.

Steps to reproduce

1. Enable feature flag

   Feature.enable(:dast_ui_redesign)

1. Go to any project /root/$PROJECT_ID/
2. Go to /root/$PROJECT_ID/-/on_demand_scans/
3. Go to the new scan form by clicking new scan
4. Create or select scanner|site profile

MR acceptance checklist

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