Helpers linter fixes
Helpers linter fixes

- Remove extra space after colon
- Ensure rule declarations are followed by an empty line
- Ensure only one property per line

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