Remove old event observers when using archive

[friedger]

When using an archive/old chain state there might be event observers in the database that are not used in the configuration.

Adding a
rm ./persistent-data/mainnet/stacks-blockchain/event_observers.sqlite should help

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.