@storybook/channel-postmessage/dist/entry.mjs

import { deprecate } from '@storybook/client-logger';
export * from '@storybook/channels/dist/postmessage/index';

deprecate("importing from @storybook/channel-postmessage is deprecated and will be removed in 8.0, please import createPostmessageChannel from @storybook/channels");