Simply go to your Setup > Installed Packages > Currency Updater and Click Uninstall.

If the uninstall button is disabled it could be for the next reasons:

1. Go to Appexchange > My Subscriptions > Select Currency Updater > Uninstall
2. You have activated Financial Force Integration. Disable it before uninstalling.
3. You have active Custom Object Rules for Dated Exchange Rates. Deactivate them before uninstalling.
4. You have custom developments, like reports, flows, or fields using our Currency Updater Objects. Please delete them before uninstalling.
5. The Schedule Job is running. Cancel manually the scheduled job, wait for the batch to finish, and try again.