Cut redundant noStroke()

It's not necessary to have both noStroke() methods here; just one will do. :)

Also, the code snippet in the text uses white circles:

```
fill(255,10);
```

…but the code example uses black circles on a while background:

```
fill(0, 10);
```

It may be useful to either change the example here and screenshot to sync up, or change the text snippet.