Update dependency @ember/optional-features to v2

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
@ember/optional-features	^1.0.0 -> ^2.0.0

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Release Notes

emberjs/ember-optional-features

### [`v2.0.0`](https://togithub.com/emberjs/ember-optional-features/blob/master/CHANGELOG.md#v200-2020-08-27) [Compare Source](https://togithub.com/emberjs/ember-optional-features/compare/v1.3.0...v2.0.0) ##### :boom: Breaking Change - [#​238](https://togithub.com/emberjs/ember-optional-features/pull/238) Drop Node 8 support. ([@​rwjblue](https://togithub.com/rwjblue)) ##### :rocket: Enhancement - [#​242](https://togithub.com/emberjs/ember-optional-features/pull/242) Update dependencies to latest versions. ([@​rwjblue](https://togithub.com/rwjblue)) ##### :house: Internal - [#​249](https://togithub.com/emberjs/ember-optional-features/pull/249) Drop util.promisify usage. ([@​rwjblue](https://togithub.com/rwjblue)) - [#​248](https://togithub.com/emberjs/ember-optional-features/pull/248) Re-roll yarn.lock. ([@​rwjblue](https://togithub.com/rwjblue)) - [#​247](https://togithub.com/emberjs/ember-optional-features/pull/247) Add prettier setup to eslint config. ([@​rwjblue](https://togithub.com/rwjblue)) - [#​245](https://togithub.com/emberjs/ember-optional-features/pull/245) Update linting package versions. ([@​rwjblue](https://togithub.com/rwjblue)) - [#​243](https://togithub.com/emberjs/ember-optional-features/pull/243) Update automated release setup. ([@​rwjblue](https://togithub.com/rwjblue)) - [#​240](https://togithub.com/emberjs/ember-optional-features/pull/240) Drop TravisCI (in favor of GitHub Actions) ([@​rwjblue](https://togithub.com/rwjblue)) ##### Committers: 2 - Robert Jackson ([@​rwjblue](https://togithub.com/rwjblue)) - [@​dependabot-preview\[bot\]](https://togithub.com/apps/dependabot-preview)

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