kiji-schema: SCHEMA-737. Update stability annotations for 1.4.0 release

issue: https://jira.kiji.org/browse/SCHEMA-737
review: https://review.kiji.org/r/1765
commit: https://github.com/kijiproject/kiji-schema/commit/2ce0c55bb337412d1fc91aa83dd34cccd0d600cd