ShaderChunk: Improved fog_fragment mediump workaround comment.

src/renderers/shaders/ShaderChunk/fog_fragment.glsl

@@ -1,6 +1,8 @@
 #ifdef USE_FOG
 
-	// divide then multiply by max component to try to avoid saturating mediump precision
+	// float fogDepth = length( vFogPosition );
+	// mediump support: divide then multiply by max component
+
 	vec3 fogPositionAbs = abs( vFogPosition );
 	float fogMaxComponent = max( fogPositionAbs.x, max( fogPositionAbs.y, fogPositionAbs.z ) );
 	float fogDepth = length( vFogPosition / fogMaxComponent ) * fogMaxComponent;