Fix getopts parsing for -6 and -q

[xxhhlk]

Summary
Fix getopts parsing so -6 is treated as a flag (not as an option with an argument), and declare that -q expects a value per usage.

Background / Problem
When using -6 (Force IPv6), subsequent options are ignored. Example:

tcpping -6 -n -C -x 1 api.bilibili.com

Expected: -n, -C, -x should apply (fping-style output with -C, one sample with -x 1).
Actual: -6 consumes the next flag (e.g., -n), option parsing stops early, and output falls back to default traceroute lines.

Root Cause
In the getopts string, -6 is mistakenly defined as requiring an argument:

getopts Zdhzq46:w:cr:nNFSAEi:f:l:m:p:s:x:CM:o
             ^

The : after 6 makes -6 consume the next token.

Fix
Remove the : after 6, and add : after q since -q expects a value per usage:

getopts Zdhzq:46w:cr:nNFSAEi:f:l:m:p:s:x:CM:o

Testing
Manually tested:

tcpping -6 -n -C -x 1 api.bilibili.com

Output format matches -C and -x 1 as expected.

Note
This PR description (including the proposed fix) was generated by AI for reference and has been manually tested.