Remove unused function

Found by ICC
builtinindexingsupport.cpp(96): warning #177: function "<unnamed>::WriteTaskFileForDiagnostics::processedDiagnostics" was declared but never referenced

Change-Id: I7de033f80b0e4431b7f1ffff13fa7bd62338aa50
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@theqtcompany.com>

src/plugins/cpptools/builtinindexingsupport.cpp

@@ -93,8 +93,6 @@ public:
                m_processedDiagnostics, qPrintable(m_file.fileName()));
     }
 
-    int processedDiagnostics() const { return m_processedDiagnostics; }
-
     void process(const CPlusPlus::Document::Ptr document)
     {
         using namespace CPlusPlus;