Change National Statistics to Accredited Official Statistics

[unoduetre]

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Follow these steps if you are doing a Rails upgrade.

What

Office for National Statistics are changing the way that statistics are presented to users.
That means that statistics that are currently referred to as National Statistics will become Accredited Official Statistics and will have a new badge image associated with them.

Here’s an example of one of the pages:
https://www.gov.uk/government/statistics/births-in-england-and-wales-2022-refreshed-populations

Tasks for homepage

1. Replace the image in government-frontend
2. Update the image alt-text in government-frontend
3. Update the display name in the locale files, including the Welsh translation, in government-frontend

Why

So users see the most up to date branding and know to trust this page

Trello ticket

Screenshots

Before

After

[beccapearce]

All the code changes look good to me!

[unoduetre]

This PR is waiting for the final confirmation of the icon sizes and one of the translations.