title: Recharts turn off tooltip for specific Line
body: <p>I have a <code>LineChart</code> with N lines. One line is fixed (straight line with a fixed y-axis value and same x-axis values as all other lines, the time value). In most cases, there's only the fixed line and just one other line with values that change. Both display correctly, but when I hover over them, the Tooltip shows data for the fixed line. I need to stop displaying the fixed line data point inside the Tooltip and start showing only the other line's data (which gets displayed ok when there's no fixed line on the chart).</p>
  
  <p>The Tooltip is just:</p>
  
  <pre><code>&lt;Tooltip
    contentStyle={{ fontSize: 12 }}
    labelStyle={{ fontSize: 12 }}
  /&gt;
  </code></pre>
  
  <p>The fixed line is:</p>
  
  <pre><code>&lt;Line
    key="fixed-key"
    isAnimationActive={false}
    dot={false}
    type="linear"
    dataKey="value"
    data={fixedData}
    connectNulls
    activeDot={false}
    legendType="rect"
    name="Threshold"
  /&gt;
  </code></pre>
  
  <p>and the dynamic line is almost the same, just a few extra props (might be worth mentioning that this line gets it's data from the data passed directly to the parent component, the <code>LineChart</code>:</p>
  
  <pre><code>&lt;Line
    key={`line-data-${id}`}
    isAnimationActive={false}
    dot={false}
    type="linear"
    dataKey={id}
    connectNulls
    stroke={lineColor || colorIndex[index]}
    activeDot={{ r: 5 }}
    legendType="rect"
    name={widgetLabel || formatLabel(metric)}
    strokeDasharray={lineType === 'dashed' ? '1 1' : null}
  /&gt;
  </code></pre>
  
  <p>So, to reiterate - the chart itself works fine, the only issue is the Tooltip component showing data for the first line, instead of just the second one - don't know how to do that, to omit a line from the Tooltip display.</p>
  
  <p>Is this possible in Recharts?</p>