[Documentation] Epic - remove classic examples from API docs for Ember 4

[jenweber]

In Ember 4, we want to show only Octane-style examples in our API docs. We need to find all the places we are still using old syntax and fix it by mid September. To help with this issue, comment with which page of the API docs you looked over, and include a link to an issue if you find anything that needs to be fixed.

The first line of your commit message and the PR description should have [DOC beta] at the beginning. This will help make sure it gets into the 4.0 release.

A check means it has a PR ready to merge, even if it is not yet merged.

• Macros - [DOC beta] remove classic syntax examples from macros #19740
• Reduce computed - help wanted! Remove "Classic Example" from packages/@ember/object/lib/computed/reduce_computed_macros.js
• Add a note to classic component docs that it is deprecated (lots of things may link to it)
• Service
• Template helpers (https://api.emberjs.com/ember/4.3/classes/Ember.Templates.helpers)
• Can anyone help us find more things that should be updated? Read over some of the docs you use the most and see if they follow Octane patterns, see if they used deprecated APIs, or if they use APIs that are being removed in Ember 4. You can find details about what is in (and not in) Ember 4 here: https://blog.emberjs.com/the-road-to-ember-4-0/

[lifeart]

likely this error should be transferred ember-learn/guides-source#1719 here

[knownasilya]

@jenweber just submitted a PR for the reduced computed file.

[jenweber]

Thank you @knownasilya!