Deprecation warning on Ember 3.4 from use of sendAction

[ghost]

This line in ember-popper-base.js triggers deprecation warnings in Ember 3.4.

ember-popper/addon/components/ember-popper-base.js

Line 255 in 462532b

this.sendAction('registerAPI', this._getPublicAPI());

Can we change it to this.registerAPI(this._getPublicAPI()), given that closure actions are the way now and sendAction is deprecated?

I note the eslint-disable ember/closure-actions currently applied, not sure if there was a rationale for this though.

[kybishop]

This was a holdover from 1.11 support, but I'm comfortable dropping that support now. Will come up with a PR to do so, or accept #92 if we can get the tests green ;)

[kybishop]

closed in #94