…must be an int (dunglas)

This PR was merged into the 4.2-dev branch.

Discussion
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[FrameworkBundle] metadata_update_threshold default value must be an int

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | yes
| New feature?  | no <!-- don't forget to update src/**/CHANGELOG.md files -->
| BC breaks?    | no     <!-- see https://symfony.com/bc -->
| Deprecations? |no <!-- don't forget to update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tests pass?   | yes    <!-- please add some, will be required by reviewers -->
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

The type of the default config value is not in sync with the typehint added to `MetadataBag::__construct()`, so you get an error by default (at least when using strict types):

```
Type error: Argument 2 passed to Symfony\Component\HttpFoundation\Session\Storage\MetadataBag::__construct() must be of the type integer, string given, called in var/cache/test/ContainerEZ62jzd/getSession_Storage_MockFileService.php on line 23 (Behat\Testwork\Call\Exception\FatalThrowableError)
```

Commits
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b7e7c46 [FrameworkBundle] metadata_update_threshold default value must be an int