release: move OCI to ORACLE

This allows future releng tooling to use OCI for the industry
standard Open Container Initiative tooling, reducing potential
for confusion.

Approved by: cperciva
Reviewed by: emaste
Differential Revision: https://reviews.freebsd.org/D46975

MFC after: 3 days
Sponsored by: SkunkWerks, GmbH

(cherry picked from commit 1be84d745bcc11b766ac1fa03afd2c8ea8771737)