fix: only reply to CTCP message if it's not a reply message itself

[heavyjoost]

🚀 Changes proposed by this PR

This fixes some issues I had where it would reply to a CTCP message even though that message was already a reply itself. Normally this probably is not an issue but when using a multiclient bouncer (ZNC in my case), this causes an infinite loop.

🧰 Type of change

• Bug fix (non-breaking change which fixes an issue).

📝 Notes to reviewer

Basically adds a if ctcp.Reply check just like the CTCP PING/PONG messages already had.

🤝 Requirements

• ✍ I have read and agree to this projects Code of Conduct.
• ✍ I have read and agree to this projects Contribution Guidelines.
• ✍ I have read and agree to the Developer Certificate of Origin.
• 🔎 I have performed a self-review of my own changes.
• 🎨 My changes follow the style guidelines of this project.

• 💬 My changes as properly commented, primarily for hard-to-understand areas.
• 📝 I have made corresponding changes to the documentation.
• 🧪 I have included tests (if necessary) for this change.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 9 lines in your changes missing coverage. Please review.

Project coverage is 53.88%. Comparing base (3842a06) to head (f8f3579).
Report is 5 commits behind head on master.

Files	Patch %	Lines
ctcp.go	0.00%	8 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #70      +/-   ##
==========================================
+ Coverage   53.75%   53.88%   +0.13%     
==========================================
  Files          16       16              
  Lines        2733     2741       +8     
==========================================
+ Hits         1469     1477       +8     
- Misses       1139     1143       +4     
+ Partials      125      121       -4     

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[lrstanley]

Need to fix my CI flow, but tests LGTM locally.

Thanks!