fix output type for Slice kernel

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

@@ -24,7 +24,7 @@ namespace Aidge {
 template<class I, class O>
 void SliceImpl_cpu_forward_kernel(const Slice_Op::Attrs &attrs, const std::vector<DimSize_t>&inputDims, const void *input_, void *output_){
     const I* input = static_cast<const I*>(input_);
-    I* output = static_cast<I*>(output_);
+    O* output = static_cast<O*>(output_);
 
     const std::size_t nbDims = inputDims.size();
     std::vector<DimSize_t> dims = inputDims;