Amend NONE state changes related to DAST Site Validation

Related &4871 (closed)

What does this MR do?

This MR

• amends a newly added NONE state to DAST site validation enum.
• replaces the wrongly used PENDING state with NONE state
  • NONE signifies a DAST validation does not exist and it's also the initial state for a DAST Site Profile
  • PENDING signifies a DAST validation process has started but not yet picked by the validation service

Screenshots (strongly suggested)

No Visual Changes

Does this MR meet the acceptance criteria?

Conformity

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