Bot API 6.8

[noplanman]

https://core.telegram.org/bots/api-changelog#august-18-2023

• Added the field story to the Message entity for messages with forwarded stories. Currently, it holds no information.
• Added the field voter_chat to the PollAnswer entity, to contain channel chat voters in Polls. For backward compatibility, the field user in such objects will contain the user 136817688 (@Channel_Bot).
• Added the field emoji_status_expiration_date to the Chat entity.
• Added the method unpinAllGeneralForumTopicMessages.
• Increased to 512 characters the maximum length of the startapp parameter in direct Web App links.