The portion of the law you quoted in your post (the legal definition of a switchblade per TX law) is still intact. What has been eliminated is a subsequent portion of law that says possessing, manufacturing, transporting, repairing, or selling the item described in the definition is a crime.
It's worth making the distinction that switchblades were never (and still aren't) "illegal knives", they were "prohibited weapons" under the old law. The new law defines them but does not restrict them beyond the display restrictions for pawnbrokers.
I can't find anything in the remaining law that would make butterfly knives illegal.
Below is the new law, as nearly as I can provide it. Basically any reference to switchblade knives was removed from 46.05.
Sec. 46.01. DEFINITIONS. In this chapter:
...
6) "Illegal knife" means a:
(A) knife with a blade over five and one-half inches;
(B) hand instrument designed to cut or stab another by being thrown;
(C) dagger, including but not limited to a dirk, stiletto, and poniard;
(D) bowie knife;
(E) sword;
or
(F) spear.
(7) "Knife" means any bladed hand instrument that is capable of inflicting serious bodily injury or death by cutting or stabbing a person with the instrument.
...
(11) "Switchblade knife" means any knife that has a blade that folds, closes, or retracts into the handle or sheath and that opens automatically by pressure applied to a button or other device located on the handle or opens or releases a blade from the handle or sheath by the force of gravity or by the application of centrifugal force. The term does not include a knife that has a spring, detent, or other mechanism designed to create a bias toward closure and that requires exertion applied to the blade by hand, wrist, or arm to overcome the bias toward closure and open the knife.
...
Sec. 46.15. NONAPPLICABILITY.
...
(e) The provisions of Section 46.02 prohibiting the carrying of an illegal knife do not apply to an individual carrying a bowie knife or a sword used in a historical demonstration or in a ceremony in which the knife or sword is significant to the performance of the ceremony.
...
Sec. 371.179. DISPLAYS OF CERTAIN WEAPONS PROHIBITED. A pawnbroker may not display for sale in a storefront window or sidewalk display case or depict on a sign or advertisement in such a way that the item, sign, or advertisement may be viewed from a street:
...
(2) a dirk; (Define or delete!)
(3) a dagger; (Define or delete!)
...
(6) a sword cane;
(7) knuckles made of metal or any other hard substance; or
(8) a switchblade, springblade, or throwblade knife.