Activity.endedAtTime appears to note recognize datetime objects

[jakebeal]

I get the following error from an apparently valid file, which has successfully loaded an RDF DateTime object into an Activity.endedAtTime:

Validation failed: Invalid. sbol-12403:� Strong Validation Error:� The endedAtTime property of an Activity object is OPTIONAL and MAY contain a DateTime. �Reference: SBOL Version 2.3.0 Section 12.8.1 on page 73 :� https://synbiohub.org/public/igem/igem2sbol� Validation failed.

File that fails to validate correctly:
BBa_J23101.xml.txt