Overleaf/services/web/frontend/stylesheets/components/menu-bar.scss

.menu-bar-toggle {
  border: none;
  border-radius: var(--border-radius-base);
  padding: var(--spacing-02);
  font-size: var(--font-size-03);
  line-height: var(--line-height-03);
  font-weight: 400;
  box-sizing: border-box;

  &.dropdown-toggle::after {
    display: none;
  }
}