Test for 404 when dast scanner and site profiles dont exist

What does this MR do?

this merge request adds tests that check the case when a dast_{site,scanner}_profile exists in a rails controller.

Related Issue(s)

• #249088 (closed)

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry technical debt
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done