Upgrade Vue Resource to 1.0.3 to fix HTTP case problems

Breaking changes to update references for:

• Changed Request.headers to Headers object
• Changed Response.headers to Headers object
• Changed Response.body property to provide processed body data as Object, Blob, string
• Changed Response methods text(), json() and blob() to return a Promise

What does this MR do?

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #27056 (closed)

EE Version: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/1591