Git: Small simplification to Gerrit "plugin" setup

The indirection is not needed. It's not really stand-alone, and not
touched before GitPlugin::initialize().

Change-Id: If8552dc69ff9efa18a3f1d6d998a8f28ab65e501
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/git/gerrit/gerritplugin.h

@@ -29,11 +29,12 @@ class GerritServer;
 class GerritPlugin : public QObject
 {
     Q_OBJECT
+
 public:
-    explicit GerritPlugin(QObject *parent = nullptr);
+    GerritPlugin();
     ~GerritPlugin() override;
 
-    void initialize(Core::ActionContainer *ac);
+    void addToMenu(Core::ActionContainer *ac);
 
     static Utils::FilePath gitBinDirectory();
     static QString branch(const Utils::FilePath &repository);