remove siteconfig from require-dev

Author: lekoala

composer.json

@@ -27,7 +27,6 @@
     "require-dev": {
         "phpunit/phpunit": "^9.5",
         "squizlabs/php_codesniffer": "^3.5",
-        "silverstripe/siteconfig": "^5",
         "silverstripe/admin": "^2",
         "openspout/openspout": "^4",
         "phpoffice/phpspreadsheet": "^1.26"