Fix video tracking

[andysellick]

⚠️ This repo is Continuously Deployed: make sure you follow the guidance ⚠️

What

Fix video tracking on AB test variants of:

• https://www.gov.uk/log-in-file-self-assessment-tax-return
• https://www.gov.uk/pay-self-assessment-tax-bill/pay-weekly-monthly

by doing the following:

• replaces the existing markup with the markup of the govspeak component, so that when rendered it will initialise the component JS correctly and include GA4 video tracking
• not the best way of doing our components but limited by how this page is rendered

I can't get the AB variant to work locally so I've not been able to fully test this, although I've inserted the markup into a visible page and it seems to be correct.

Related to alphagov/frontend#3931

Why

Video tracking is required on these pages.

Visual changes

Shouldn't be any, although the video may appear slightly differently/better.

Trello card: https://trello.com/c/rHlNjPxe/775-video-tracking-not-working-on-a-b-test-pages

[davidtrussler]

This looks like it does what's required WRT tracking (and is more elegant than the current implementation). Nice! 👍