Remove unnecessary cast. Fixes root-project#13421 (root-project#14284)

* Remove unnecessary cast. This should fix root-project#13421

* Removed too much

tmva/tmva/inc/TMVA/RBatchGenerator.hxx

@@ -97,7 +97,7 @@ public:
 
       // Create tensor to load the chunk into
       fChunkTensor =
-         std::make_unique<TMVA::Experimental::RTensor<float>>((std::vector<std::size_t>){fChunkSize, fNumColumns});
+         std::make_unique<TMVA::Experimental::RTensor<float>>(std::vector<std::size_t>{fChunkSize, fNumColumns});
    }
 
    ~RBatchGenerator() { DeActivate(); }