Update mikey179/vfsstream requirement from 1.6.11 to 1.6.12

Updates the requirements on [mikey179/vfsstream](https://github.com/bovigo/vfsStream) to permit the latest version.
- [Release notes](https://github.com/bovigo/vfsStream/releases)
- [Changelog](https://github.com/bovigo/vfsStream/blob/v1.6.12/CHANGELOG.md)
- [Commits](bovigo/vfsStream@v1.6.11...v1.6.12)

---
updated-dependencies:
- dependency-name: mikey179/vfsstream
  dependency-version: 1.6.12
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

composer.json

@@ -16,7 +16,7 @@
     },
     "require-dev": {
         "infection/infection": "^0.18",
-        "mikey179/vfsstream": "1.6.11",
+        "mikey179/vfsstream": "1.6.12",
         "phpunit/phpunit": "~9.0"
     },
     "autoload": {