Don't log import latency every time the task times out

[michaelkedar]

The workers log latency regardless of whether the task finished or not: https://github.com/google/osv.dev/blob/01173bfd380841914bda13453d3a1853395924de/docker/worker/worker.py#L623-L628

This messes with our import latency SLO monitoring, since jobs repeatedly get processed & timed out until it's processed correctly or dead-lettered.

We should also add a subscription to the dead letter topic to monitor failed imports

[github-actions[bot]]

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