no need for fragDepth in image shader

src/mol-gl/shader-code.ts

@@ -136,7 +136,7 @@ export const DirectVolumeShaderCode = ShaderCode('direct-volume', direct_volume_
 
 import image_vert from './shader/image.vert';
 import image_frag from './shader/image.frag';
-export const ImageShaderCode = ShaderCode('image', image_vert, image_frag, { fragDepth: true });
+export const ImageShaderCode = ShaderCode('image', image_vert, image_frag);
 
 //
 

src/mol-gl/shader/image.frag.ts

@@ -111,11 +111,7 @@ void main() {
         if (imageData.a < 0.05)
             discard;
 
-        #ifdef enabledFragDepth
-            gl_FragColor = packDepthToRGBA(gl_FragDepthEXT);
-        #else
-            gl_FragColor = packDepthToRGBA(gl_FragCoord.z);
-        #endif
+        gl_FragColor = packDepthToRGBA(gl_FragCoord.z);
     #elif defined(dRenderVariant_color)
         if (imageData.a < 0.05)
             discard;