Consolidate iModel-backed phrasing within IonSnapService documentation

[markschlosseratbentley]

Feature

See this comment: #13682 (comment)

Now that #13682 has merged, we should consider the iModel-backed phrasing the IonSnapService documentation uses. Once we know across-the-board what phrasing we will be using to describe these kinds of assets, we should update the IonSnapService documentation as appropriate.

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