Update phpstan/phpstan requirement from 0.12.94 to 0.12.99 (#60)

Updates the requirements on [phpstan/phpstan](https://github.com/phpstan/phpstan) to permit the latest version.
- [Release notes](https://github.com/phpstan/phpstan/releases)
- [Commits](phpstan/phpstan@0.12.94...0.12.99)

---
updated-dependencies:
- dependency-name: phpstan/phpstan
  dependency-type: direct:development
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

composer.json

@@ -8,7 +8,7 @@
 		"php-64bit": "*"
 	},
 	"require-dev": {
-		"phpstan/phpstan": "0.12.94",
+		"phpstan/phpstan": "0.12.99",
 		"phpstan/extension-installer": "^1.0",
 		"phpstan/phpstan-strict-rules": "^0.12.4"
 	},