Make the OK button the default in the settings migration dialog.

common/dialogs/dialog_migrate_settings.cpp

@@ -2,7 +2,7 @@
  * This program source code file is part of KiCad, a free EDA CAD application.
  *
  * Copyright (C) 2020 Jon Evans <jon@craftyjon.com>
- * Copyright (C) 2020 KiCad Developers, see AUTHORS.txt for contributors.
+ * Copyright (C) 2020-2021 KiCad Developers, see AUTHORS.txt for contributors.
  *
  * This program is free software: you can redistribute it and/or modify it
  * under the terms of the GNU General Public License as published by the
@@ -32,6 +32,7 @@ DIALOG_MIGRATE_SETTINGS::DIALOG_MIGRATE_SETTINGS( SETTINGS_MANAGER* aManager ) :
 
     m_btnCustomPath->SetBitmap( KiBitmap( BITMAPS::small_folder ) );
 
+    m_standardButtonsOK->SetDefault();
     GetSizer()->SetSizeHints( this );
     Centre();
 }