Update the date of birth pattern
Update the date of birth pattern

- Remove the duplicate heading and legend text
- Add missing form-label classes to the labels

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