cli: fix rad inbox clear output — heartwood

If multiple ids are specified for rad inbox clear, it would report that only 1 item was cleared, when in fact multiple were.

This was found to be due to the SQL code returning a change count of 1. This is likely due to the way the statement is being reset each time. The sqlite library does not seem to easily support the usage of IN in a WHERE clause. So instead, the count is aggregated in the loop and returned instead.

 ```
 ``` ~alice
 $ rad inbox clear
 $ rad inbox clear 1 2
 ✓ Cleared 2 item(s) from your inbox
 $ rad inbox
 Your inbox is empty.

                 .db
                 .prepare("DELETE FROM `repository-notifications` WHERE rowid = ?")?;
             // N.b. we need to keep the count manually since the change count
             // will always be `1` because of each reset.
             let mut count = 0;
             for id in ids {
                 stmt.bind((1, *id as i64))?;
                 stmt.next()?;
                 stmt.reset()?;
                 count += self.db.change_count();
             }
             Ok(self.db.change_count())
             Ok(count)
         })
     }