refactor: keep the scheduled message API error type internal

ScheduledMessageAPIError is only used by getScheduledMessageErrorReason, so
it no longer needs to be part of the public types.

Author: NikolaGoranNaumovski

src/scheduledMessages/errors.ts

@@ -1,6 +1,7 @@
 import { ErrorFromResponse, ScheduledMessageErrorReason } from '../types';
 import type { APIErrorResponse } from '../types';
-import type { ScheduledMessageAPIError } from './types';
+
+type ScheduledMessageAPIError = ErrorFromResponse<APIErrorResponse>;
 
 const NOT_FOUND_STATUS = 404;
 

src/scheduledMessages/types.ts

@@ -1,7 +1,3 @@
-import type { APIErrorResponse, ErrorFromResponse } from '../types';
-
-export type ScheduledMessageAPIError = ErrorFromResponse<APIErrorResponse>;
-
 export type ScheduledMessageLimits = {
   maxLeadTimeSeconds: number;
   maxPerChannel: number;