title: Marks in mui range Sliders gets duplicated because of two children with the same key
body: <p>I am experiencing a bug from the range slider of mui wherein the marks get duplicated when both of the thumb slider reached the farthest right.</p>
  <p>Initially my slider is like this:</p>
  <p><img src="https://i.stack.imgur.com/3XTFi.png" alt="enter image description here" /></p>
  <p>Once I slide both of the thumbs to the farthest right an error will occur on the console:</p>
  <p><img src="https://i.stack.imgur.com/QnkPx.png" alt="enter image description here" /></p>
  <p><img src="https://i.stack.imgur.com/Zy72Y.png" alt="enter image description here" /></p>
  <p>Then the mark would get duplicated like this:<br />
  <img src="https://i.stack.imgur.com/NaRwH.png" alt="enter image description here" /></p>
  <p>The cause was that the SliderUnstyled uses the value from marks as its key. Because of this, when both of the thumbs reach the farthest right, both of them would have a value of 100 which triggers the error of duplicate keys.</p>
  <p>Here is also a link of a codesandbox from another developer facing the same issue: <a href="https://codesandbox.io/s/material-demo-forked-tlu40e?file=/demo.js" rel="nofollow noreferrer">https://codesandbox.io/s/material-demo-forked-tlu40e?file=/demo.js</a></p>
  <p>I saw a similar issue from Github from this link: <a href="https://github.com/mui/material-ui/issues/31960" rel="nofollow noreferrer">https://github.com/mui/material-ui/issues/31960</a></p>
  <p>One solution there was to modify the SliderUnstyled.js file from &quot;material-ui/packages/mui-base/src/SliderUnstyled/SliderUnstyled.js&quot; wherein you need to change the key to the mark's index instead of the mark's value.</p>
  <p>I've tried the solution from this <a href="https://github.com/mui/material-ui/pull/33526/commits/4ff58040654a4b75aa86691194df80bd2abd87b8" rel="nofollow noreferrer">https://github.com/mui/material-ui/pull/33526/commits/4ff58040654a4b75aa86691194df80bd2abd87b8</a> but I just want to ask if there is another solution to this issue wherein modifying the SliderUnstyled.js is not necessary.</p>