Draft changelog: X Activity API subscription expiration

[mintlify]

Summary

Adds a Sep 22, 2026 changelog entry announcing the optional expires_at field on X Activity API subscriptions.

Changes

• New <Update> entry at the top of changelog.mdx summarizing expires_at behavior, refresh-via-recreate semantics, and the PUT limitation
• Links to the new Subscription expiration section

Context

Follows #441, which documented expires_at on the X Activity API introduction page.

[mintlify]

Preview deployment for your docs. Learn more about Mintlify Previews.

Project	Status	Preview	Updated
x-corp	🟢 Ready	View Preview	Sep 22, 2026, 5:45 PM

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}