Replace wxGenericAboutDialog::Init() with member initialization

No real changes, just modernize the code a bit.

include/wx/generic/aboutdlgg.h

@@ -42,13 +42,11 @@ public:
     // --------------------------------
 
     // default ctor, you must use Create() to really initialize the dialog
-    wxGenericAboutDialog() { Init(); }
+    wxGenericAboutDialog() = default;
 
     // ctor which fully initializes the object
     wxGenericAboutDialog(const wxAboutDialogInfo& info, wxWindow* parent = nullptr)
     {
-        Init();
-
         (void)Create(info, parent);
     }
 
@@ -80,9 +78,6 @@ protected:
 #endif // wxUSE_COLLPANE
 
 private:
-    // common part of all ctors
-    void Init() { m_sizerText = nullptr; }
-
 #if !wxUSE_MODAL_ABOUT_DIALOG
     // An explicit handler for deleting the dialog when it's closed is needed
     // when we show it non-modally.
@@ -90,7 +85,7 @@ private:
     void OnOK(wxCommandEvent& event);
 #endif // !wxUSE_MODAL_ABOUT_DIALOG
 
-    wxSizer *m_sizerText;
+    wxSizer *m_sizerText = nullptr;
 };
 
 // unlike wxAboutBox which can show either the native or generic about dialog,