Avoid warning on empty expressions

For some reason, Q_UNUSED includes already a semicolon, adding one
on the user side creates an additional empty statement.

Change-Id: I9c5e8fac381345a60792cb75e2938fd53958d3b0
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/diffeditor/diffeditor.cpp

@@ -138,7 +138,7 @@ void DescriptionEditorWidget::setDisplaySettings(const DisplaySettings &ds)
 
 void DescriptionEditorWidget::setMarginSettings(const MarginSettings &ms)
 {
-    Q_UNUSED(ms);
+    Q_UNUSED(ms)
     TextEditorWidget::setMarginSettings(MarginSettings());
 }