tweak per-group transparency cutoff

src/mol-gl/shader/chunks/assign-material-color.glsl.ts

@@ -86,7 +86,7 @@ export const assign_material_color = `
 // apply per-group transparency
 #if defined(dTransparency) && (defined(dRenderVariant_pick) || defined(dRenderVariant_color))
     float ta = 1.0 - vTransparency;
-    if (vTransparency < 0.2) ta = 1.0; // hard cutoff looks better
+    if (vTransparency < 0.09) ta = 1.0; // hard cutoff looks better
 
     #if defined(dRenderVariant_pick)
         if (ta < uPickingAlphaThreshold)