Update dependency ember-source to ~5.6.0

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
ember-source (source)	~5.5.0 -> ~5.6.0

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Release Notes

emberjs/ember.js (ember-source)

### [`v5.6.0`](https://togithub.com/emberjs/ember.js/blob/HEAD/CHANGELOG.md#v560-January-22-2024) [Compare Source](https://togithub.com/emberjs/ember.js/compare/v5.5.0...v5.6.0) - [#​20595](https://togithub.com/emberjs/ember.js/pull/20595) \[BUGFIX] An addon re-export should always be a JavaScript file - [#​20603](https://togithub.com/emberjs/ember.js/pull/20603) \[BUGFIX] Internal templates should be strictMode - [#​20605](https://togithub.com/emberjs/ember.js/pull/20605) \[BUGFIX] Move babel-plugin-ember-template-compilation to dependencies - [#​20570](https://togithub.com/emberjs/ember.js/pull/20570) \[CLEANUP] Remove all traces of named outlets code

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