Fixed template declaration

src/operator/ConvImpl.cpp

@@ -183,7 +183,4 @@ void Aidge::ConvImpl_cuda<DIM>::backward() { printf("Not implemented yet.\n"); }
 
 
 // Template declarations
-void ConvImpl_cuda_template_declaration ()
-{
-    Aidge::ConvImpl_cuda<2> ConvImpl_cuda2(Aidge::Conv_Op<2>());
-}
+template class Aidge::ConvImpl_cuda<2>;