fix(quick-start): use props instead of args in route template code example

[jayjayjpg]

This updates the code example in the Quick Start section, explaining how to pass properties to a component to use the this. syntax instead of argument syntax @.

As far as I'm aware, properties are only prefixed with an @ when they refer to arguments passed into a component. In this code example the property model is used in a route's template though, therefore this.model should be used instead of @model.

[chancancode]

This was an intentional change (#1044), part of emberjs/rfcs#523. As of emberjs/ember.js#18363, @model is a full-fledged argument passed into the route template (in addition to being on the JavaScript controller class as this.model). However, there is a bit of a temporary problem, in that this only works on canary at the moment, and the Octane blueprints have been updated to track beta releases recently. This should be resolved next week when beta switches to 3.14.

[jayjayjpg]

@chancancode Thanks a lot for the detailed explanation!