Fix PHPStan error

[staabm]

fixes

➜  type-perfect git:(main) ✗ vendor/bin/phpstan            
Xdebug: [Step Debug] Could not connect to debugging client. Tried: localhost:9003 (through xdebug.client_host/xdebug.client_port).
Note: Using configuration file /Users/m.staab/dvl/type-perfect/phpstan.neon.
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  Line   src/Printer/CollectorMetadataPrinter.php                                                                       
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  91     Parameters should have "PhpParser\Node\Stmt\ClassMethod|string" types as the only types passed to this method  
         🪪  typePerfect.narrowPublicClassMethodParamType                                                               
         at src/Printer/CollectorMetadataPrinter.php:91                                                                 
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[TomasVotruba]

Thanks