If there is someone waiting to adopt your child then you will likely be relieved of support obligations -just giving up your rights to quit paying child support is not going to happen
The State of Texas has a quaint notion that all children deserve to have two parents supporting them (even if one of those parents doesn't give a damn about them). Therefore, it is hard to just "give up your rights" unless another adult is going to step in a be a parent to your child. Supporting a child is part of being a parent. You play, you pay.