Remove any IE8-10 specific styles and stylesheet(s)

[vanitabarrett]

What

Remove any IE8 specific styles, as we're dropping support for IE in a future breaking release.

Why

We have decided to reduce support for IE11 in GOV.UK Frontend and drop support completely for IE8-10. We shared these proposed changes with the frontend community in GDS and across government, and have only received positive feedback.

We will make these changes in a future breaking release of GOV.UK Frontend (likely v5.0.0).

Who needs to work on this

Developers; possibly Tech Writer

Who needs to review this

Developers

Done when

• Remove any IE8-10 specific styles/stylesheets
• Update/remove any associated documentation

[querkmachine]

We've decided to handle the docs changes after all of the IE removals have taken place, rather than doing them piecemeal, so I'm closing this as done.

[romaricpascal]

For refrerence, the documentation updates are tracked by: alphagov/govuk-frontend-docs#188 😊