Redirect to on-demand scan form after editing a DAST profile

What does this MR do and why?

This ensures that users are properly redirected to the on-demand scan form after editing or creating DAST site/scanner profiles from there.

Screenshots or screen recordings

Before	After
	after

How to set up and validate locally

1. Navigate to a project's on-demand scans list at /:namespace/:project/-/on_demand_scans#/saved.
2. If you haven't created a DAST scan profile yet, click New DAST scan and follow the instructions.
3. Edit any DAST scan in the list.
4. Select a scanner profile from the dropdown, then click the pencil icon to edit it OR select Create new scanner profile from the dropdown.
5. Save the scanner profile OR cancel the form.
   • You should be redirected back to the DAST scan edit form.
6. Repeat last two steps with site profiles.
   • The behavior should be the same.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #349830 (closed)