fix variable name

[lhy11009]

I think this is cos_lat instead of cos_long

Also checked all the other places where longitude and latitude are mentioned and they seem all correct.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.31%. Comparing base (545bb15) to head (128f811).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #687      +/-   ##
==========================================
+ Coverage   98.30%   98.31%   +0.01%     
==========================================
  Files         107      107              
  Lines        7358     7358              
==========================================
+ Hits         7233     7234       +1     
+ Misses        125      124       -1     

Files	Coverage Δ
source/world_builder/utilities.cc	97.35% <100.00%> (ø)

... and 1 file with indirect coverage changes

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[github-actions]

Benchmark	Main	Feature	Difference (99.9% CI)
Slab interpolation simple none	1.015 ± 0.005 (s=455)	1.018 ± 0.005 (s=433)	+0.2% .. +0.4%
Slab interpolation curved simple none	1.010 ± 0.011 (s=446)	1.012 ± 0.011 (s=447)	+0.0% .. +0.5%
Spherical slab interpolation simple none	1.166 ± 0.006 (s=385)	1.164 ± 0.005 (s=390)	-0.3% .. -0.1%
Slab interpolation simple curved CMS	1.060 ± 0.004 (s=412)	1.055 ± 0.003 (s=442)	-0.5% .. -0.3%
Spherical slab interpolation simple CMS	1.610 ± 0.017 (s=268)	1.610 ± 0.017 (s=294)	-0.3% .. +0.3%
Spherical fault interpolation simple none	1.173 ± 0.006 (s=396)	1.173 ± 0.010 (s=374)	-0.1% .. +0.2%
Cartesian min max surface	2.307 ± 0.016 (s=205)	2.308 ± 0.023 (s=188)	-0.2% .. +0.4%
Spherical min max surface	7.225 ± 0.028 (s=58)	7.220 ± 0.029 (s=69)	-0.3% .. +0.2%

[MFraters]

Makes sense, thanks for the fix!