Deleted unnecessary files

packages/slack/src/interfaces/http-errors.ts

@@ -1,12 +0,0 @@
-import { HttpError } from 'http-errors';
-
-export class CustomHttpError extends Error {
-
-  httpError: HttpError
-
-  constructor(httpError: HttpError) {
-    super(httpError.message);
-    this.httpError = httpError;
-  }
-
-}