Issue 584: Replace errant reference to non-existent concept owl:Datatype

[ajnelson-nist]

This Pull Request resolves all requirements of Issue #584 .

Coordination

• [x] Pull Request is against correct branch
• [x] Pull Request is in, or reverted to, Draft status before Solutions Approval vote has passed
• [x] CI passes in UCO feature branch against develop
• [x] CI passes in UCO current unstable branch (bb6bee3)
• [x] CI passes in CASE current unstable branch tracking UCO's unstable as submodule (4663451)
• [x] Impact on SHACL validation reviewed for CASE-Corpora
• [x] Impact on SHACL validation remediated for CASE-Corpora
• [x] Impact on SHACL validation reviewed for CASE-Examples
• [x] Impact on SHACL validation remediated for CASE-Examples (N/A)
• [x] Impact on SHACL validation reviewed for casework.github.io
• [x] Impact on SHACL validation remediated for casework.github.io (N/A)
• [x] Milestone linked
• [x] Solutions Approval vote logged on corresponding Issue (N/A)

[ajnelson-nist]

This PR is ready for review and merge.