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/texteditor/codeassist/genericproposalmodel.cpp

@@ -337,7 +337,7 @@ FuzzyMatcher::CaseSensitivity
 
 bool GenericProposalModel::isSortable(const QString &prefix) const
 {
-    Q_UNUSED(prefix);
+    Q_UNUSED(prefix)
 
     if (m_currentItems.size() < kMaxSort)
         return true;