fix(challenges): add code input space for final d3 challenge

Author: Alex Swiontek

challenges/04-data-visualization/data-visualization-with-d3.json

@@ -2836,6 +2836,9 @@
             "       .attr(\"y\", (d) => yScale(d[1]))",
             "    ",
             "    const xAxis = d3.axisBottom(xScale);",
+            "    // Add your code below this line",
+            "    const yAxis = undefined;",
+            "    // Add your code above this line",
             "    ",
             "    svg.append(\"g\")",
             "       .attr(\"transform\", \"translate(0,\" + (h - padding) + \")\")",