Complexity graph is not shown in HTML report dashboard

Graph placeholder is present, but the graph itself is not drawn. The following error appears in JS console when opening the dashboard:

```
TypeError: chart.scatter.onlyCircles is not a function
```

Manual removal of _chart.scatter.onlyCircles()_ call from html template fixes the problem. I guess it's something wrong with d3.js version.

The issue seems to be present since version 2.1.0
