Clang: Remove unused enum 'SendMode'

Change-Id: Ia95aface60d6f00db5e38d28fc3bf2a3fd7d4406
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/clangcodemodel/clangbackendipcintegration.h

@@ -156,8 +156,6 @@ signals: // for tests
     void backendReinitialized();
 
 private:
-    enum SendMode { RespectSendRequests, IgnoreSendRequests };
-
     void initializeBackend();
     void initializeBackendWithCurrentData();
     void registerCurrentProjectParts();