OCDS 1.2: Updates to guidance outside documentation

[jpmckinney]

Using this issue to log changes we'll need to make once 1.2 is deployed.

Use case guide

• Update indicator UC0047 to use tender.datePublished (see add tender.datePublished field #1324)

[odscjen]

Update Glossary crosswalk

[jpmckinney]

I think it's okay to leave the crosswalk as a historical artifact.