K_convention to represent cheb polynomial order

[SherylHYX]

Due to popular request to match the code convention to the K parameter in papers, I have updated K parameter in MagNet and MSGNN codes to represent the Cheb polynomial order instead of filter size, which is filter size minus 1.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.59%. Comparing base (10f54d8) to head (86f9f33).
Report is 6 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #64   +/-   ##
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  Coverage   99.59%   99.59%           
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  Files          77       77           
  Lines        3728     3728           
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  Hits         3713     3713           
  Misses         15       15           

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