minor symfony#52208 [Intl] Hide generated files in GitHub diffs and statistics (GromNaN)

This PR was submitted for the 6.4 branch but it was merged into the 5.4 branch instead.

Discussion
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[Intl]  Hide generated files in GitHub diffs and statistics

| Q             | A
| ------------- | ---
| Branch?       | 6.4
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Issues        | -
| License       | MIT

See [Customizing how changed files appear on GitHub](https://docs.github.com/en/repositories/working-with-files/managing-files/customizing-how-changed-files-appear-on-github).

> To keep certain files from displaying in diffs by default, or counting toward the repository language, you can mark them with the linguist-generated attribute in a `.gitattributes` file.

This makes diff easier to read. Generated files diff can still be displayed, but they are hidden by default in PR like symfony#52183

Example from an other project:
<img width="795" alt="image" src="https://github.com/symfony/symfony/assets/400034/a2ebf6f9-0aa8-48da-b453-38c8a6d08cb2">

Commits
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bfa9ee0 Hide generated files in GitHub diffs and statistics

Author: fabpot

.gitattributes

@@ -4,3 +4,4 @@
 /src/Symfony/Component/Messenger/Bridge export-ignore
 /src/Symfony/Component/Notifier/Bridge export-ignore
 /src/Symfony/Component/Runtime export-ignore
+/src/Symfony/Component/Intl/Resources/data/*/* linguist-generated=true