Fix older items possibly disappearing on timeline updates (#17980)

In some rare cases, when receiving statuses out of order from the streaming
API then polling from the REST API, it was possible for the
`expandNormalizedTimeline` function to remove older items from the timeline.

This commit ensures that any item from the replaced slice that is older
than the oldest item retrieved from the API gets added back to the replaced
slice.

0 files changed, 0 insertions, 0 deletions