message: docs: expand changeset scope
  `@backstage/backend-test-utils` has been updated to use a plugin
  name which starts with an alphabetical character, changeset now
  includes this package.
diff: ---
  '@backstage/backend-common': minor
  '@backstage/create-app': minor
  +'@backstage/backend-test-utils': minor
  ---
  Deprecates `SingleConnectionDatabaseManager` and provides an API compatible database
  