[beta] Remove `propertyBraceExpansion` feature flags for 1.4.0.
[beta] Remove `ember-metal-run-bind` feature flags for 1.4.0.
[beta] Remove `with-controller` feature flags for 1.4.0.
Merge pull request #4322 from rjackson/remove-feature-flags

Remove Feature Flags for 1.4.0.