Gui: use utf-8 encoding for saving recorded macros

FCMacros always have the header "# -*- coding: utf-8 -*".
But the QTextStream class in Qt5 does not always use utf-8 for saving the text file.

src/Gui/Macro.cpp

@@ -80,6 +80,9 @@ bool MacroFile::commit()
 
     // sort import lines and avoid duplicates
     QTextStream str(&file);
+#if QT_VERSION < QT_VERSION_CHECK(6,0,0)
+    str.setCodec("UTF-8");
+#endif
     QStringList import;
     import << QString::fromLatin1("import FreeCAD");
     QStringList body;