Update supported Ember CLI version in addon blueprint

[bertdeblock]

More info

[kellyselden]

I don't think this is right. Addons work in current - 1 of ember-cli. Otherwise every ember-cli-update run would "break" addons, requiring everyone update their version of ember-cli.

[rwjblue]

Addons work in current - 1 of ember-cli.

Sorry, what does this mean? Addons should work with all supported versions of ember-cli, which is roughly the same support schedule as ember-source. By the time this branch is published (3.27.0 in ~ 8 weeks) that would be only ember-cli@3.20 ember-cli@3.24 and ember-cli@3.27 (which is what this documentation update implies).

[kellyselden]

Oh my bad I misread. I see now that it is tracking the ember version with -2 LTS. I revoke my concern :)