Directly assign a boolean value in deprecated-features

Author: wagenet

packages/@ember/deprecated-features/index.ts

@@ -3,4 +3,5 @@
 // These versions should be the version that the deprecation was _introduced_,
 // not the version that the feature will be removed.
 
-export const ASSIGN = !!'4.0.0-beta.1';
+/** Introduced in 4.0.0-beta.1 */
+export const ASSIGN = true;