refactor: Remove unused method

This method is not used. The setup reader instead directly uses the
convertFromJson method from the JSON mixin.

src/blackcore/data/globalsetup.h

@@ -199,9 +199,6 @@ namespace BlackCore::Data
         //! Build the full dbdata directory URL from shared URL
         static BlackMisc::Network::CUrl buildDbDataDirectoryUrl(const BlackMisc::Network::CUrl &candidate);
 
-        //! Object initialized by JSON file
-        static CGlobalSetup fromJsonFile(const QString &fileNameAndPath, bool acceptCacheFormat);
-
     private:
         int m_dbHttpPort = 80; //!< port
         int m_dbHttpsPort = 443; //!< SSL port