Update phpstan/phpstan-mockery requirement from 0.12.12 to 0.12.13

Updates the requirements on [phpstan/phpstan-mockery](https://github.com/phpstan/phpstan-mockery) to permit the latest version.
- [Release notes](https://github.com/phpstan/phpstan-mockery/releases)
- [Commits](phpstan/phpstan-mockery@0.12.12...0.12.13)

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

composer.json

@@ -34,7 +34,7 @@
         "phpstan/phpstan-nette": "0.12.16",
         "nepada/phpstan-nette-tester": "0.3.1",
         "spaze/phpstan-disallowed-calls": "1.4.0",
-        "phpstan/phpstan-mockery": "0.12.12",
+        "phpstan/phpstan-mockery": "0.12.13",
         "php-parallel-lint/php-parallel-lint": "1.2",
         "nepada/coding-standard": "7.3",
         "nette/bootstrap": "^3.0@dev",