core/apis/errors: rename to error and don't export Error type

packages/core/src/api/apis/definitions/error.ts

@@ -20,7 +20,7 @@ import ApiRef from '../ApiRef';
  * Mirrors the javascript Error class, for the purpose of
  * providing documentation and optional fields.
  */
-export type Error = {
+type Error = {
   name: string;
   message: string;
   stack?: string;

packages/core/src/api/apis/definitions/index.ts

@@ -20,4 +20,4 @@
 //
 // If you think some API definition is missing, please open an Issue or send a PR!
 
-export * from './errors';
+export * from './error';