message: remove duplicated conditional
  (we check for the same thing inside applyChange)
diff: @@ -69,7 +69,7 @@ class Schema {
  }
  await contentType.validate(pendingChange, context);
  - if (this.schemaLoader.ownTypes().includes(type)) {
  +
  // Safety check: the change we're about to approve is a schema
  // change. The following will deliberately blow up if the new
  // schema hits a bug anywhere in schema instantiation. Better to
  @@ -80,7 +80,6 @@ class Schema {
  return newSchema;
  }
  }
  - }
  _validateDocumentStructure(document, context) {
  if (!document.type) {
  