Add deprecation announcement on editor field in workspaces graphql schema

MR: Deprecations announcement on editor field (!174897 - merged)

Description

Remove references for editor field on workspaces (!167673 - merged) has marked the editor field as deprecated, in keeping with the process we should add an announcement,

Acceptance Criteria

• Deprecation announcement highlighting removal of the editor field from the graphql API in milestone 18.0 with reasons