Remove deprecated editor field from GraphQL API

MR: Pending

References

Remove graphql fields `editor` from workspace t... (#508155)

Description

We need to remove references of this field in the graphQL API in %18.0 , per the deprecation guidelines in https://docs.gitlab.com/ee/api/graphql/#deprecation-and-removal-process

This is a follow up to this MR: Remove references for editor field on workspaces (!167673 - merged) where we deprecated the editor field from the API in milestone %17.5

See details in this thread: !167673 (comment 2147134342)

Acceptance Criteria

• Remove API doc references for this field
• Remove it from the create workspace mutation
• Remove it from the workspace type