504 when requesting 100 notices

History here: https://chat.canonical.com/canonical/pl/4m1kkwir1f8x3fabk9b4dtgyjy

At the time of writing, https://ubuntu.com/security/notices.json works, https://ubuntu.com/security/notices.json?limit=20 works, but https://ubuntu.com/security/notices.json?limit=100 produces a 504 error. It's not clear right now if this has been the case for a long time or is a recent development.

Requesting 100 notices is probably not an unreasonable ask. We should see if it's possible to provide this. If it's not possible we should make it clear the maximum number that's supported by the API for querying at any one time.