Install PHPStan through composer

It has isolated dependencies nowadays and it will be helpful for other developers, who probably expect it to be installed that way and do not want to use Nix.

Author: jtojnar

composer.json

@@ -11,7 +11,8 @@
     "require-dev" : {
         "friendsofphp/php-cs-fixer": "^3.0",
         "php-parallel-lint/php-parallel-lint": "^1.0",
-        "symfony/phpunit-bridge": "^6.2"
+        "symfony/phpunit-bridge": "^6.2",
+        "phpstan/phpstan": "^1.12"
     },
     "autoload": {
         "psr-4": { "Fossar\\GuzzleTranscoder\\": "src/" }

flake.nix

@@ -34,7 +34,6 @@
             # Composer and PHP.
             php
             php.packages.composer
-            php.packages.phpstan
           ];
         };
       };