Constants: Remove deprecated code. (#27480)

Removes `TwoPassDoubleSide` in favor of `Material.forceSinglePass` (#25239).

Author: CodyJasonBennett

src/constants.js

@@ -13,7 +13,6 @@ export const VSMShadowMap = 3;
 export const FrontSide = 0;
 export const BackSide = 1;
 export const DoubleSide = 2;
-export const TwoPassDoubleSide = 2; // r149
 export const NoBlending = 0;
 export const NormalBlending = 1;
 export const AdditiveBlending = 2;