You can remove a quota for a specific target by removing the quotas file entry for that target. Depending on what other quotas you have set up, you then need to resize or reinitialize quotas.
If you have a default quota or default tracking quota in place for the quota type you modified, you can use the quota resize command to cause Data ONTAP to reread the quotas file. Otherwise, reinitialize quotas using the quota off and quota on commands for the volume for which you modified the quota.