I ran out of quota too soon in this billing period, and I don't need the current errors in Sentry anymore. Is there a way to delete events to free up quota?

We are unable to reset your quota or delete events that have already been accepted.

Once an error event is accepted by Sentry and counted against your error quota, deleting that event from the project will not free up or restore your quota. The error quota reflects the total number of error events your account is allowed to accept over a certain period.
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This policy is in place because we incur costs associated with data ingestion.

If you still need to accept new events for this billing period, you can either set an on-demand budget/pay-as-you-go or increase your reserved quota.

You can read more about Quota Management here.