Deleting Constraints
You can delete constraints using the Delete Constraint
                
 tool in the Constraints group or using the
                option from the mini-toolbar.
Using the Delete Constraint tool:
Select Delete Constraint
                
 in the Constraints group. The Delete
                    Constraint tool is available when Show Constraint Tips
                
 is enabled.
Select the constraint to be deleted. In case of multiple constraints, click the drop-down and then select the constraint to be deleted.
Using the option from the mini-toolbar: