[Documentation] Registering a Library uses deprecated global Ember in the docs of 3.27

[johanrd]

📙 Describe the Issue

The 3.27 docs on registering a library uses the global Ember, even though the global Ember is deprecated in 3.27:

Registering a Library
If you would like to add your own application or library to the list, you can register it using:
Ember.libraries.register(libraryName, libraryVersion);

➕ Additional Context

This makes e.g. apps running with Ember Simple Auth get the following error message on Ember ^3.27.0 (mainmatter/ember-simple-auth#2309):
DEPRECATION: Usage of the Ember Global is deprecated. You should import the Ember module or the specific API instead. [deprecation id: ember-global] See https://deprecations.emberjs.com/v3.x/#toc_ember-global for more details.