data-test on docs-header/link breaks with ember-test-selectors@^2.0.0

[sglanzer]

ember-test-selectors@^2.0.0 breaks on this line

https://github.com/ember-learn/ember-cli-addon-docs/blob/master/addon/components/docs-header/template.hbs#L26

due to binding on a tagless component

https://github.com/ember-learn/ember-cli-addon-docs/blob/master/addon/components/docs-header/link/component.js#L8

[sglanzer]

Looks like #271 is intended to fix this