revisit log severity of bulk insert errors during initial sync oplog application

Since SERVER-32335, we started grouping inserts during initial sync oplog application. Depending on to the timing of the collection cloning phase and the starting optime of the oplog application phase, we may get DuplicateKey errors from ApplierHelper::InsertGroup and subsequently degrade into doing single inserts. We should revisit the severity of the error log messages from ApplierHelpers::InsertGroup.