remove dev dependencies because there is no CI

Author: thomas-kl1

composer.json

@@ -38,13 +38,6 @@
         "ext-mbstring": "*"
     },
     "require-dev": {
-        "phpunit/phpunit": "^7.0",
-        "phpmd/phpmd": "^2.6",
-        "sebastian/phpcpd": "^2.0",
-        "squizlabs/php_codesniffer": "^3.2",
-        "friendsofphp/php-cs-fixer": "^2.10",
-        "pdepend/pdepend": "^2.5",
-        "phpstan/phpstan": "@stable"
     },
     "autoload": {
         "psr-4": {