Inspector: Avoid using "notehead type" to mean different things

The Note Inspector contained two properties with similar names:

- "Notehead type"
- "Notehead type (visual only)"

Now the latter is relabelled as "Override visual duration" to prevent
confusion and to give a better indication of what it actually does.

src/inspector/view/qml/MuseScore/Inspector/notation/notes/HeadSettings.qml

@@ -141,7 +141,7 @@ FocusableItem {
 
                 NoteheadTypeSelector {
                     id: noteHeadTypeSection
-                    titleText: qsTrc("inspector", "Notehead type (visual only)")
+                    titleText: qsTrc("inspector", "Override visual duration")
                     propertyItem: root.model ? root.model.headType : null
 
                     navigationName: "NoteHeadTypeSection"