tidy #65809 [FrameworkBundle][SecurityBundle] Stop committing the functional test apps' generated schema.json (nicolas-grekas)

This PR was merged into the 8.2 branch.

Discussion
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[FrameworkBundle][SecurityBundle] Stop committing the functional test apps' generated schema.json

| Q             | A
| ------------- | ---
| Branch?       | 8.2
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Issues        | -
| License       | MIT

Since #65394, booting a functional test app in debug mode dumps `schema.json` next to the `reference.php` the config reference pass already produced, into the fixture `app/config/` directory. `deleteTmpDir()` cleans up `reference.php` but `schema.json` was forgotten, so every functional run leaves a ~7000-line untracked file behind, and `git add` sweeps it into unrelated commits (it slipped into #65394 itself, and almost into #65798/#65799).

Nothing reads the committed copy: `JsonSchemaConfigDumpPassTest` dumps into a temp dir, and the `lint:yaml` tests write their own. This removes the accidentally committed FrameworkBundle copy and deletes the byproduct in both `deleteTmpDir()` implementations, like `reference.php`.

Commits
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118f4795675 [FrameworkBundle][SecurityBundle] Stop committing the functional test apps' generated schema.json