You can delete user-defined debug probes using the delete_hw_probe Tcl command.
For example, to delete a probe foobar created earlier using create_hw_probe do the following:
delete_hw_probe [get_hw_probes foobar -of_objects [get_hw_ilas -of_objects
[get_hw_devices xc7k325t_0] -filter {CELL_NAME=~"i_fast_ila"}]]