remove unused code

[gammazero]

• Include change to clone messages more efficiently.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 61.52%. Comparing base (261c4eb) to head (5f74f77).
Report is 1 commits behind head on main.

@@            Coverage Diff             @@
##             main     #967      +/-   ##
==========================================
+ Coverage   61.47%   61.52%   +0.04%     
==========================================
  Files         249      254       +5     
  Lines       31333    31400      +67     
==========================================
+ Hits        19262    19318      +56     
- Misses      10498    10505       +7     
- Partials     1573     1577       +4     

Files with missing lines	Coverage Δ
bitswap/message/message.go	78.59% <100.00%> (-1.22%)	⬇️

... and 12 files with indirect coverage changes

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