UnitTests: Cleanup SupportiveTranslationUnitInitializer test

Change-Id: I0c43baeb13fe2a1004622267deb4e588f941d254
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/tools/clangbackend/source/clangjobqueue.h

@@ -56,6 +56,7 @@ public:
 
 public: // for tests
     JobRequests &queue();
+    const JobRequests &queue() const;
     int size() const;
     void prioritizeRequests();