CppEditor: Fix a warning about unused arg

Amends 0e04f40fa7

Change-Id: I5acd596670bb3332f6e6d1984ec5ccb75c3e161a
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/clangformat/clangformatbaseindenter.cpp

@@ -562,6 +562,7 @@ Utils::ChangeSet ClangFormatBaseIndenter::replacements(QByteArray buffer,
 Utils::EditOperations ClangFormatBaseIndenter::format(const TextEditor::RangesInLines &rangesInLines,
                                                       FormattingMode mode)
 {
+    Q_UNUSED(mode)
     QTC_ASSERT(!m_fileName.isEmpty(), return {});
     if (rangesInLines.empty())
         return {};