Use simpler Plugin::initialize() when feasible

Change-Id: I567965d266f20526bda9f823e31a04b354d53fb1
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/clangformat/clangformatplugin.h

@@ -12,7 +12,7 @@ class ClangFormatPlugin : public ExtensionSystem::IPlugin
     Q_OBJECT
     Q_PLUGIN_METADATA(IID "org.qt-project.Qt.QtCreatorPlugin" FILE "ClangFormat.json")
 
-    bool initialize(const QStringList &arguments, QString *errorString) final;
+    void initialize() final;
     QVector<QObject *> createTestObjects() const override;
 };