You can hack the internal component via querySelector

[JackVeromeev]

here is the code

const style = document.createElement('style');
style.innerText = `
  div[b2b_buyer_product_details-summary_summary].quantity-and-list {
    display: none !important;
  }
`;

this.template.querySelector('.container').appendChild(style);

[JackVeromeev]

For sure, it will require the <div class="container" lwc:dom="manual"></div> tag inside your component