Hello,
Unfortunately, it is not possible to delete a public IP that is attached to a resource without first detaching it from that resource.
To detach a public IP from a resource, you will need to have access to the resource and be able to modify its settings. If you do not have access to the resource, you will not be able to detach the public IP from it.
One option you could consider is contacting the owner of the subscription where the resource is located and requesting that they detach the public IP from the resource. If you are unable to do this, you may need to consider alternative solutions, such as creating a new public IP and attaching it to the resource instead of the one you are unable to delete.
Good luck!