Bump phpstan/extension-installer from 1.1.0 to 1.2.0

Bumps [phpstan/extension-installer](https://github.com/phpstan/extension-installer) from 1.1.0 to 1.2.0.
- [Release notes](https://github.com/phpstan/extension-installer/releases)
- [Commits](phpstan/extension-installer@1.1.0...1.2.0)

---
updated-dependencies:
- dependency-name: phpstan/extension-installer
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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Author: dependabot[bot]