`axis.showline` does not work with `trace.zorder`

Codepen: https://codepen.io/emilykl-code/pen/ZYEEXvw?editors=1111

Axis lines are not drawn when one of the traces on the plot has a zorder property.

Figure definition:

Plotly.newPlot(
  "div1", 
  [
    {
      x: [11, 12, 13, 14, 15],
      y: [9, 10, 12, 16, 24],
      zorder: 2,
    },
    {
      x: [15, 14, 13, 12, 11],
      y: [9, 10, 12, 16, 24],
    }
  ], 
  {
    title: { text: "A Plotly Chart" },
    xaxis: { showline: true },
    yaxis: { showline: true },
  }
);

Expected (axes lines visible):
(note -- blue trace should be in front)

Actual:

Start with the CodePen reproduction and the Plotly.newPlot figure definition in the issue, using the axis showline and trace zorder options. Compare the expected and actual images while tracing how those options are rendered. Done means both axis lines remain visible and the zordered blue trace stays in front.