Make it possible to discard reconciliation errors

In #6006, @ostephens wrote:

For me I think that if the error doesn't need any further follow up I'd want to be able to get rid of it. Is there going to be some mechanism by which the user can clear any reconciliation errors that have been stored? (except a later successful reconciliation)? Perhaps a menu option to clear errors in the same way we have one that clears reconciliation data?

Proposed solution

The operations which match a cell to a reconciliation candidate (or match it to a new item) should clear the error. This would mean that one could get rid of an error by either:

• matching the cell to a manually-selected candidate
• matching the cell to a new item
• discarding reconciliation info in the cell (making the cell unreconciled)

Alternatives considered

Make it possible to clear the error without making a reconciliation judgment? I am not sure why one would want to do that, since the three options above seem sufficient to me.

Additional context

Follow-up to #6006.

Start by tracing the reconciliation operations described in the issue: matching a cell to a selected candidate, matching it to a new item, and discarding reconciliation information. Check the existing reconciliation-error behavior and tests, if present; done means each of those actions clears the stored error without requiring a separate menu action.