Update patterns in song editor after shifting their notes by semitones in piano roll. (#3961)

After shifting notes up/down, call rearrangeAllNotes() to sort notes and dataChanged()
to update the pattern the Song Editor.

src/gui/editors/PianoRoll.cpp

@@ -961,6 +961,9 @@ void PianoRoll::shiftSemiTone( int amount ) // shift notes by amount semitones
 		}
 	}
 
+	m_pattern->rearrangeAllNotes();
+	m_pattern->dataChanged();
+
 	// we modified the song
 	update();
 	gui->songEditor()->update();