Advance RFC #0858 `"Deprecate ember-mocha"` to Stage Recommended

[emberjs-rfcs-bot]

Advance #0858 to the Recommended Stage

Summary

This pull request is advancing the RFC to the Recommended Stage.

• PR to Accepted Stage: #0858
• PR to Ready For Release Stage
• PR to Released Stage

An FCP is required before merging this PR to advance.

Recommended Stage Summary

The "Recommended" stage is the final milestone for an RFC. It provides a signal to the wider community to indicate that a feature has been put through its ecosystem paces and is ready to use. To reach the "Recommended" stage, the following should be true: If appropriate, the feature is integrated into the tutorial and the guides prose. API documentation is polished and updates are carried through to other areas of API docs that may not directly pertain to the feature. If the proposal replaces an existing feature, the addon ecosystem has largely updated to work with both old and new features. If the proposal updates or replaces an existing feature, high-quality codemods are available. If needed, Ember debugging tools as well as popular IDE support have been updated to support the feature. If the feature is part of a suite of features that were designed to work together for best ergonomics, the other features are also ready to be "Recommended". Any criteria for "Recommended" for this proposal that were established in the Ready For Release stage have been met. An FCP is required to enter this stage. Multiple RFCs may be moved as a batch into "Recommended" with the same PR.

Checklist to move to Recommended

• [x] Any criteria for "Recommended" for this proposal that were established in the Ready For Release stage have been met
• [x] If appropriate, the feature is integrated into the tutorial and the guides prose. API documentation is polished and updates are carried through to other areas of API docs that may not directly pertain to the feature.
• [ ] ~If the proposal replaces an existing feature, the addon ecosystem has largely updated to work with both old and new features.~
• [ ] ~If the proposal updates or replaces an existing feature, high-quality codemods are available~
• [ ] ~If needed, Ember debugging tools as well as popular IDE support have been updated to support the feature.~
• [ ] ~If the feature is part of a suite of features that were designed to work together for best ergonomics, the other features are also ready to be "Recommended".~
• [x] This PR has been converted from a draft to a regular PR and the Final Comment Period label has been added to start the FCP

Criteria for moving to Recommended (required)

A set of criteria for moving this RFC to the Recommended Stage, following release:

• [x] Removal of references to ember[-cli]-mocha in all documentation

[mansona]

I created a PR to remove the last few things mentioning mocha from the guides: https://github.com/ember-learn/guides-source/pull/1964

[mansona]

And this removes it from the cli guides: https://github.com/ember-learn/cli-guides/pull/304