ProjectExplorer: Remove FileNode's isGenerated constructor bool

Use setter of base class, similar to setListInProject() before.

Change-Id: Id620f0084a5dec0410f29c80f8f6393a6bcd5050
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/pythoneditor/pythoneditorplugin.cpp

@@ -471,7 +471,7 @@ class PythonFileNode : public FileNode
 public:
     PythonFileNode(const Utils::FileName &filePath, const QString &nodeDisplayName,
                    FileType fileType = FileType::Source)
-        : FileNode(filePath, fileType, false)
+        : FileNode(filePath, fileType)
         , m_displayName(nodeDisplayName)
     {}