Remove restoreScroll option

[jon-kirwan]

What

Remove restoreScroll option

See https://github.com/alphagov/govuk_publishing_components/blob/main/app/assets/javascripts/component_guide/accessibility-test.js#L27

Why

The option has been removed. See dequelabs/axe-core#2388

Anything else

I'm pretty sure that the following test is related, which checks the scroll position is 0 before and after the test, and can be removed.

https://github.com/alphagov/govuk_publishing_components/blob/main/spec/javascripts/govuk_publishing_components/AccessibilityTestSpec.js#L87-L101

  it('should not scroll the page', function (done) {
    var bigElement = '<div style="height: 1000px; width: 100px;"></div>'

    addToDom(
      bigElement + '<a href="#">Low contrast</a>' + bigElement,
      'a { background: white; color: #ddd }'
    )

    expect(window.scrollY).toBe(0, 'should start at top of the page')

    AccessibilityTest(TEST_SELECTOR, function () {
      expect(window.scrollY).toBe(0, 'should end at top of the page')
      done()
    })
  })

The removed restoreScroll option reset the scroll position when checking scrollable elements for color-contrast violations. The test is no longer needed following performance improvements to how the color-contrast rule works which doesn't rely on scrolling the element into view.