Tidy up Ember Data 2.x upcoming deprecations

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There are a number of "Upcoming" deprecations listed in the Ember Data 2.x page: https://deprecations.emberjs.com/ember-data/v2.x/.
The following work needs to be accomplished:

1. Review each deprecation marked as Upcoming
   1.a. If they have been released, update the target version appropriately.
   1.b. If they are still scheduled to be released, move them to 3.x
   1.c. If they have not been released, remove them

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cc @Windvis