Update phpstan/phpstan-mockery requirement from ^0.12.7 to ^0.12.12

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@0.12.7...0.12.12)

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

composer.json

@@ -30,7 +30,7 @@
         "phpstan/phpstan-nette": "^0.12.10",
         "nepada/phpstan-nette-tester": "^0.3.1",
         "spaze/phpstan-disallowed-calls": "^1.0.1",
-        "phpstan/phpstan-mockery": "^0.12.7",
+        "phpstan/phpstan-mockery": "^0.12.12",
         "php-parallel-lint/php-parallel-lint": "^1.2",
         "nepada/coding-standard": "^7.3",
         "nette/bootstrap": "^3.0@dev",