[#31] Fix XPaths used in date_order rules at 2.01
[#31] Fix XPaths used in date_order rules at 2.01

The XPaths used in date_order `less` and `more` were previously incorrect
as they did not refer to valid XPaths containing dates at v2.01.

IATI/IATI-Rulesets,IATI/IATI-Rulesets