Build(deps): bump phpstan/phpstan from 1.6.4 to 1.7.8 in /.dev-tools

Bumps [phpstan/phpstan](https://github.com/phpstan/phpstan) from 1.6.4 to 1.7.8.
- [Release notes](https://github.com/phpstan/phpstan/releases)
- [Changelog](https://github.com/phpstan/phpstan/blob/1.7.x/CHANGELOG.md)
- [Commits](phpstan/phpstan@1.6.4...1.7.8)

---
updated-dependencies:
- dependency-name: phpstan/phpstan
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

.dev-tools/composer.json

@@ -8,7 +8,7 @@
         "mi-schi/phpmd-extension": "^4.3.0",
         "phpmd/phpmd": "^2.12.0",
         "phpstan/extension-installer": "^1.1.0",
-        "phpstan/phpstan": "^1.6.4",
+        "phpstan/phpstan": "^1.7.8",
         "phpstan/phpstan-phpunit": "^1.1.1",
         "phpstan/phpstan-strict-rules": "^1.2.2",
         "squizlabs/php_codesniffer": "^3.6.2",