Add USE_ANISOTROPY to prefixVertex in WebGLProgram. (#26716)

src/renderers/webgl/WebGLProgram.js

@@ -494,6 +494,7 @@ function WebGLProgram( renderer, cacheKey, parameters, bindingStates ) {
 			parameters.displacementMap ? '#define USE_DISPLACEMENTMAP' : '',
 			parameters.emissiveMap ? '#define USE_EMISSIVEMAP' : '',
 
+			parameters.anisotropy ? '#define USE_ANISOTROPY' : '',
 			parameters.anisotropyMap ? '#define USE_ANISOTROPYMAP' : '',
 
 			parameters.clearcoatMap ? '#define USE_CLEARCOATMAP' : '',