Write the function setCircleRadii to change the radii of the circles
to be 10 times the bound value.
<body>
<div>
<svg id="svg">
<circle cx="100" cy="50" r="5" fill="red"></circle>
<circle cx="130" cy="50" r="5" fill="green"></circle>
<circle cx="160" cy="50" r="5" fill="blue"></circle>
</svg>
</div>
<script>
var data = [1, 2, 3];
d3.selectAll("circle").data(data);
setCircleRadii(d3.selectAll("circle")); // write this function
</script>
</body>