use default for sequence deserialize

[patternmachine]

The with = "terra_opt_u64_format" only applies when the actual field is present. So if the server reply does not include a sequence field (eg for a new account) then deserialization will just fall without the default

[2022-02-05T01:47:50Z ERROR do_swap] Reqwest HTTP(s) Error
[2022-02-05T01:47:50Z ERROR do_swap] because: error decoding response body: missing field `sequence` at line 1 column 144
[2022-02-05T01:47:50Z ERROR do_swap] because: missing field `sequence` at line 1 column 144

[PFC-developer]

Thanks!