fix(src/components/timeline): remove useless `Timeline.hpp` file

tests/src/components/timeline/Timeline.hpp

-#ifndef SETTINGS_MODEL_H_
-#define SETTINGS_MODEL_H_
-
-#include <QObject>
-
-#include "AccountSettingsModel.hpp"
-
-// ===================================================================
-
-class SettingsModel : public QObject {
-  Q_OBJECT
-
-public:
-  SettingsModel (QObject *parent = Q_NULLPTR);
-
-private:
-  QList<AccountSettingsModel *> accountsSettings;
-};
-
-#endif // SETTINGS_MODEL_H_