Remove unneeded shader uniform

shader/simple.vert

@@ -2,7 +2,6 @@
 uniform mat4 projMat;
 
 uniform vec2 texSizeInv;
-uniform float texOffsetX;
 uniform vec2 translation;
 
 attribute vec2 position;
@@ -14,5 +13,5 @@ void main()
 {
 	gl_Position = projMat * vec4(position + translation, 0, 1);
 
-	v_texCoord = vec2(texCoord.x + texOffsetX, texCoord.y) * texSizeInv;
+	v_texCoord = texCoord * texSizeInv;
 }