Fix GraphBLAS complex value compilation

[alugowski]

Fixes #40

[codecov]

Codecov Report

Patch coverage: 72.72% and no project coverage change.

Comparison is base (874838b) 93.46% compared to head (b3204e7) 93.46%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #41   +/-   ##
=======================================
  Coverage   93.46%   93.46%           
=======================================
  Files          23       23           
  Lines        2187     2187           
  Branches      279      279           
=======================================
  Hits         2044     2044           
  Misses        143      143           

Files Changed	Coverage Δ
include/fast_matrix_market/app/GraphBLAS.hpp	85.40% <72.72%> (ø)

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