sniffer: fix mangled lines on stdout output

[maxmouchet]

Newlines were fixed in #61 but we're still getting bad lines:

1704573826,1,::ffff:132.227.123.8,::ffff:37.61.226.8,24000,0,8,1,::ffff:62.40.98.238,1,11,0,241,172,"[(14716,0,0,11704573826,1,::ffff:132.227.123.8,::ffff:37.23.143.233,24000,0,8,1,::ffff:62.40.98.238,1,11,0,248,168,"[(62839,0,1,1)]",92,1

std::ios::sync_with_stdio(false); seems to be the culprit.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (4764ae4) 80.37% compared to head (d96956a) 80.37%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #62 +/- ## ======================================= Coverage 80.37% 80.37% ======================================= Files 23 23 Lines 1228 1228 Branches 712 712 ======================================= Hits 987 987 Misses 115 115 Partials 126 126 ```

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