Add python 3 support to decode_mars_nocrypt_log_file.py

[ChaseChoi]

Python 2 is no longer supported.

[tencent-adm]

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[StevenYan88]

本身是python 3 .10.7版本执行啊

[shawnlinboy]

LGTM.
A friendly ping to the maintainer team. Please help with landing this PR.