Move sampler3D precision definition inside #ifdef (#21531)

examples/jsm/postprocessing/LUTPass.js

@@ -31,10 +31,10 @@ const LUTShader = {
 
 
 	fragmentShader: /* glsl */`
-		precision highp sampler3D;
 
 		uniform float lutSize;
 		#if USE_3DTEXTURE
+		precision highp sampler3D;
 		uniform sampler3D lut3d;
 		#else
 		uniform sampler2D lut;