JSFiddle - React, Tailwind, and code Playground

HTML

<table border>
<tr>
    <td class="mixed-section_td">1.1</td>
    <td class="mixed-section_td">1.2</td>
    <td class="mixed-section_td">1.3</td>
</tr>
<tr>
    <td class="mixed-section_td">2.1</td>
    <td class="mixed-section_td">2.2</td>
    <td class="mixed-section_td">2.3</td>
</tr>
<tr>
    <td class="mixed-section_td">3.1</td>
    <td class="mixed-section_td">3.2</td>
    <td class="mixed-section_td">3.3</td>
</tr>
</table>

JavaScript

const deleteFirstElemsCount = 2;
let elems = Array.from(document.querySelectorAll("table tr") || []);
elems.forEach((elem,i)=>{
  if(i<deleteFirstElemsCount){
  	elem.remove();
  };
});