Remove validation from DAST site profile form

What does this MR do?

DAST site validation has been rethought and will not be part of the DAST site profile form like it was originally designed to be. This is the first step in a series of changes to move the validation to a dedicated modal accessible from the DAST profiles library.

Here, we're simply removing all of the validation logic from the DAST site profile form to clean things up.

Screenshots (strongly suggested)

Before	After

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry (this is still behind a feature flag)
• [-] Documentation (if required) (this feature is still un-documented)
• 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

Related to #280559 (closed)