fix : removed unused variable

src/operator/Concat.cpp

@@ -23,7 +23,6 @@ void Aidge::Concat_OpImpl::forward() {
     const DimSize_t axis = op.axis();
 
     assert(op.getInput(0) && "missing input in Concat operator");
-    DataType datatypeFirstInput = op.getInput(0)->dataType();
     for (IOIndex_t i = 1; i < mOp.nbInputs(); ++i) {
         assert(op.getInput(i) && "missing input in Concat operator");
         assert(op.getInput(i)->dataType() == datatypeFirstInput);