In SERVER-77269 we removed some logic from BatchWriteOp::cancelWrites that had no effect. Now that it is removed, the why parameter is no longer used, so we should just remove it and update the call sites to stop passing a value.

https://github.com/mongodb/mongo/blob/5f1b3024bf6e1d2f79e0c934a694b92929370c16/src/mongo/s/write_ops/write_op.cpp#L251

Also, the BatchWriteOp::_cancelBatches method which calls this method is not used so we can remove it as well.