Fix fmt version in aidge backend_cpu

Context

Error when including fmt/base.h during installation of aidge_backend_cpu. This is similar to aidge_core#255 (closed)

I've implemented the same fix as here aidge_core@5bd0b0e9

Modified files

• PadImpl_kernels.hpp

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

@@ -19,7 +19,7 @@
 #include <cmath>
 #include <cstddef>   // std::size_t
 #include <cstdint>   // std::int32_t
-#include <fmt/base.h>
+
 #include <stdexcept>
 #include <type_traits>