Remove unused/orphaned metadata.

Request

• Base URL
  /rest (relative, and the document was published on a file host, not at the API’s origin)
• Auth
  OAuth 2

  Authorization code/auth/authorize

  Token URL/rest/auth/token

  Scopesadmin
• TypeScript
  https://skmtc.dev/openhab/apis/openhab-rest-api/docs/items/metadata/purge/post.ts

  A function with typed inputs. Its response is checked against the schema.