[Upd] forwa Concat after removal of 'NbInputs' attribute

include/aidge/backend/cpu/operator/ConcatImpl_forward_kernels.hpp

@@ -42,11 +42,11 @@ void ConcatImpl_cpu_forward_kernel(const Concat_Op::Attrs& attrs,
     DimSize_t outputAxisValue = std::accumulate(concatAxisValues.begin(), concatAxisValues.end(), 0);
 
     DimSize_t prodDimLower = 1;
-    for (DimIdx_t i = 0; i < std::get<1>(attrs); ++i) {
+    for (DimIdx_t i = 0; i < std::get<0>(attrs); ++i) {
         prodDimLower *= dimsFirstInput[i];
     }
     DimSize_t prodDimHigher = 1;
-    for (DimIdx_t i = std::get<1>(attrs) + 1; static_cast<std::size_t>(i) < dimsFirstInput.size();
+    for (DimIdx_t i = std::get<0>(attrs) + 1; static_cast<std::size_t>(i) < dimsFirstInput.size();
          ++i) {
         prodDimHigher *= dimsFirstInput[i];
     }