Remove implicit injection

[locks]

This addon is using a deprecated functionality in the inject-storefront which causes problems in Ember 4.0.
The path forward here is to remove the instance initializer and have the users explicitly inject the service as necessary.

Context:

• Original deprecation: https://deprecations.emberjs.com/v3.x#toc_implicit-injections
• Related issue: implicit-injections deprecation is missing for v4.x series ember-learn/deprecation-app#1065.