minor #2715 [StimulusBundle] Make the JS package private (for real) (Kocal)

This PR was merged into the 2.x branch.

Discussion
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[StimulusBundle] Make the JS package private (for real)

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->
| Docs?         | no <!-- required for new features -->
| Issues        | Fix #... <!-- prefix each issue number with "Fix #", no need to create an issue if none exist, explain below instead -->
| License       | MIT

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Following #2709 and failing checks like https://github.com/symfony/ux/actions/runs/14850493570/job/41693038644?pr=2713

Commits
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625bf5e [StimulusBundle] Make the JS package private (for real)

Author: Kocal

src/StimulusBundle/assets/package.json

@@ -1,7 +1,7 @@
 {
     "name": "@symfony/stimulus-bundle",
     "description": "Integration of @hotwired/stimulus into Symfony",
-    "private": "true",
+    "private": true,
     "license": "MIT",
     "version": "2.24.0",
     "keywords": [