Resolve "Remove leftover local resolver for Design management GraphQL client"

What does this MR do?

After changing design query from local query to actually fetching data from the API in !19212 (merged) we don't need a resolver in ee/app/assets/javascripts/design_management/graphql.js.

This MR removes the mentioned resolver

Does this MR meet the acceptance criteria?

Conformity

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

Mentions #36653 (closed)