Add API::VulnerabilityFindings to OpenApi V2

What does this MR do and why?

Add API::VulnerabilityFindings to OpenAPIv2.

• ✅ Check the Parameter documentation needs to be updated
  • No updates needed.
• ✅ Check the description block needs to be updated. Ideally this should include a success entry.
  • Descriptions look fine. All entries have success.
• ✅ If the endpoint responds with an Array, use the is_array true helper
  • Done.
• Compare the parameters and description to the markdown documentation for this endpoint
  • Used "String" for swagger even though markdown docs say "Integer or String".

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

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 #377039