optmap: use unflatten instead of convolve

[ManuelHu]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 31.03448% with 20 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.90%. Comparing base (29d501d) to head (3253797).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/reboost/optmap/convolve.py	31.03%	20 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #145      +/-   ##
==========================================
- Coverage   70.12%   69.90%   -0.23%     
==========================================
  Files          33       33              
  Lines        2497     2505       +8     
==========================================
  Hits         1751     1751              
- Misses        746      754       +8     

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[gipert]

Is the code ready for production after this? If yes, can we make a new release?