In #15474 we introduced dedicated support for date ranges. As part of that
change we added a fallback of "magic" date ranges, which treats dates in
any paragraph with exactly two dates as a range. There were discussions
about migrating all such paragraphs to use the new date range element, but
it was ultimately decided against.
This change removes the fallback and, as a bonus, adds support for multiple
date ranges in the same paragraph.
