This PR was squashed before being merged into the 5.0-dev branch (closes #31671).

Discussion
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[Intl] Cleanup legacy  API

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no     <!-- see https://symfony.com/bc -->
| Deprecations? | no
| Tests pass?   | yes (including intl-data group)
| Fixed tickets | #...   <!-- #-prefixed issue number(s), if any -->
| License       | MIT
| Doc PR        | symfony/symfony-docs#... <!-- required for new features -->

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Commits
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67105d2 [Intl] Cleanup legacy  API