fix(bmc:library): sn type fix in RLP_decode_struct.py

Author: simusud

smartpy/bmc/contracts/src/RLP_decode_struct.py

@@ -32,7 +32,7 @@ def decode_bmc_message(self, rlp):
         return sp.record(src=temp_map_string.get("src"),
                          dst=temp_map_string.get("dst"),
                          svc=temp_map_string.get("svc"),
-                         sn=sp.to_int(temp_int.value),
+                         sn=temp_int.value,
                          message=temp_byt.value)