make Plotly.deleteTraces on 'surface' and 'mesh' traces work

Author: etpinard

src/traces/mesh3d/convert.js

@@ -141,7 +141,7 @@ proto.update = function(data) {
 };
 
 proto.dispose = function() {
-    this.glplot.remove(this.mesh);
+    this.scene.glplot.remove(this.mesh);
     this.mesh.dispose();
 };
 

src/traces/surface/convert.js

@@ -323,7 +323,7 @@ proto.update = function(data) {
 
 
 proto.dispose = function() {
-    this.glplot.remove(this.surface);
+    this.scene.glplot.remove(this.surface);
     this.surface.dispose();
 };