Improvement: Remove a magic number

[sandro-elsweijer]

Closes #1780

Describe your changes here:
Removes a magic number in a cmesh attribute and replaces it with the correct macro.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.06%. Comparing base (e73f517) to head (cec7af8).
Report is 194 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1779   +/-   ##
=======================================
  Coverage   74.06%   74.06%           
=======================================
  Files          99       99           
  Lines       18703    18703           
=======================================
  Hits        13852    13852           
  Misses       4851     4851           

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