Utils: Drop QProcess specific parameters from QtcProcess::finished()

Mid-term plan is to concentrate on use of QtcProcess::result()
instead which is a bit more system-agnostic.

There's quite a bit of potential for downstream cleanup by
re-using QtcProcess::exitMessage() now.

Change-Id: I3806b3f5933d96e64b7cfb18cc6c52823fddcbcd
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/cppcheck/cppcheckrunner.h

@@ -61,7 +61,7 @@ private:
     void readOutput();
     void readError();
     void handleStarted();
-    void handleFinished(int);
+    void handleFinished();
 
     CppcheckTool &m_tool;
     Utils::QtcProcess *m_process = nullptr;