always apply marker in shader

src/mol-gl/shader/chunks/apply-marker-color.glsl.ts

@@ -1,13 +1,10 @@
 export default `
-// only mark elements with an alpha above the picking threshold
-if (gl_FragColor.a >= uPickingAlphaThreshold) {
-    float marker = floor(vMarker * 255.0 + 0.5); // rounding required to work on some cards on win
-    if (marker > 0.1) {
-        if (intMod(marker, 2.0) > 0.1) {
-            gl_FragColor.rgb = mix(uHighlightColor, gl_FragColor.rgb, 0.3);
-        } else {
-            gl_FragColor.rgb = mix(uSelectColor, gl_FragColor.rgb, 0.3);
-        }
+float marker = floor(vMarker * 255.0 + 0.5); // rounding required to work on some cards on win
+if (marker > 0.1) {
+    if (intMod(marker, 2.0) > 0.1) {
+        gl_FragColor.rgb = mix(uHighlightColor, gl_FragColor.rgb, 0.3);
+    } else {
+        gl_FragColor.rgb = mix(uSelectColor, gl_FragColor.rgb, 0.3);
     }
 }
 `;