Remove abbreviation explanation in print CSS

Abbreviations currently have the term they represent added afterwards in brackets in the print styles. This is clashing with our usage, as explained in this ticket:

https://govuk.zendesk.com/agent/#/tickets/73349

Removing this style aligns our usage across media to that specified in the styleguide:

https://www.gov.uk/designprinciples/styleguide#abbreviations-and-acronyms