Yielding parentComponent=this raises computed property override deprecation

[alanlalonde]

Usage of parentComponent=this has been flagged for deprecation in favor of using manual setters. Here is the deprecation message, as it pertains to the implementation from ember-paper-stepper.

DEPRECATION: The <app-name@component:paper-step::ember733>#parentComponent computed property was just overriden. This removes the computed property and replaces it with a plain value, and has been deprecated. If you want this behavior, consider defining a setter which does it manually. [deprecation id: computed-property.override] See https://emberjs.com/deprecations/v3.x#toc_computed-property-override for more details.

As such, fixing it here would require bumping versions in whichever dependency is used by that package (it does not seem to directly depend on ember-composability-tools).

[alanlalonde]

Whoops, tricky click finger. I opened a PR that fixes the computed property by adding the recommended getter and setter, as per the deprecation guide.