Change frontend to be one word
Change frontend to be one word

This is in line with the README in the frontend toolkit repo.

gavboulton/govuk_elements,TFOH/govuk_elements,alphagov/govuk_elements,alphagov/govuk_elements,gavboulton/govuk_elements,gavboulton/govuk_elements,joelanman/govuk_elements,alphagov/govuk_elements,alphagov/govuk_elements,gavboulton/govuk_elements,TFOH/govuk_elements,joelanman/govuk_elements