Add delay for accessibility node list to be populated

Looks like there are some internal (to Chromium) changes when `aria-expanded` state changes, but adding a 100ms delay from Accordion button `.click()` to calling `page.accessibility.snapshot()` fixes the child node loop ✅

Lots of commits landing so may not need this workaround in future:

* chromium/chromium@08fed96
* chromium/chromium@c7fae74
* chromium/chromium@06f376b
* chromium/chromium@86543a2

Another one ongoing to stablise accessibility objects:
https://chromium-review.googlesource.com/c/chromium/src/+/4027071

src/govuk/components/accordion/accordion.test.js

@@ -256,6 +256,7 @@ describe('/components/accordion', () => {
           )
 
           await $element.click()
+          await page.waitForTimeout(100)
 
           await expect(getAccessibleName(page, $element)).resolves.toBe(
             'Section A , Hide this section'
@@ -274,6 +275,7 @@ describe('/components/accordion', () => {
           )
 
           await $element.click()
+          await page.waitForTimeout(100)
 
           await expect(getAccessibleName(page, $element)).resolves.toBe(
             'Test , Additional description , Hide this section'