ParserCSV: guard use of QTextStream::setCodec

QTextStream::setCodec was removed in Qt6.
https://bugreports.qt.io/browse/QTBUG-75665

src/library/parsercsv.cpp

@@ -140,9 +140,13 @@ bool ParserCsv::writeCSVFile(const QString &file_str, BaseSqlTableModel* pPlayli
 
     qDebug() << "Basepath: " << base;
     QTextStream out(&file);
-    out.setCodec("UTF-8"); // rfc4180: Common usage of CSV is US-ASCII ...
-                           // Using UTF-8 to get around codepage issues
-                           // and it's the default encoding in Ooo Calc
+    // rfc4180: Common usage of CSV is US-ASCII ...
+    // Using UTF-8 to get around codepage issues
+    // and it's the default encoding in Ooo Calc
+    // UTF-8 is the default in Qt6.
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+    out.setCodec("UTF-8");
+#endif
 
     // writing header section
     bool first = true;