Fix typo in the bdld_datum.h documentation
Fix typo in the bdld_datum.h documentation

Reviewers: da39a3ee5e6b4b0d3255bfef95601890afd80709@hversche

che2/bde,bloomberg/bde,che2/bde,bloomberg/bde,bloomberg/bde,che2/bde,bloomberg/bde,che2/bde,bloomberg/bde