Fix bug: Failed to open file volumetric_fog.fx

Author: ray-cast

Shader/textures.fxsub

@@ -33,7 +33,6 @@ texture FogMap: OFFSCREENRENDERTARGET<
 	string DefaultEffect =
 		"GroundFog*.*= ./Fog/GroundFog/ground_fog.fx;"
 		"AtmosphericFog*.*= ./Fog/AtmosphericFog/atmospheric_fog.fx;"
-		"VolumetricFog.pmx =./Fog/VolumetricFog/volumetric_fog.fx;"
 		"VolumetricCube.pmx =./Fog/VolumetricCube/volumetric_cube.fx;"
 		"VolumetricSphere.pmx =./Fog/VolumetricSphere/volumetric_sphere.fx;"
 		"* = hide;";