emberjs/ember.js v5.9.0 on GitHub

#20653 [DEPRECATION] Deprecate (action) and {{action}} in templates per RFC #1006.
#20669 [FEATURE] Make deprecations throw when the until for ember-source has passed per RFC #0830.
#20656 / #20664 [BUGFIX] Upgrade router_js to support exactOptionalPropertyTypes
#20658 Upgrade glimmer-vm to v0.92
#20678 Address a missed deprecation introduced in #20658