Fix a typo

[danieldouglas92]

I noticed that constraints was spelled incorrectly in a few places!

[github-actions]

Benchmark	Main	Feature	Difference (99.9% CI)
Slab interpolation simple none	1.123 ± 0.019 (s=410)	1.124 ± 0.019 (s=394)	-0.3% .. +0.5%
Slab interpolation curved simple none	1.116 ± 0.009 (s=398)	1.118 ± 0.009 (s=410)	-0.1% .. +0.3%
Spherical slab interpolation simple none	1.095 ± 0.010 (s=417)	1.094 ± 0.008 (s=408)	-0.3% .. +0.1%
Slab interpolation simple curved CMS	1.167 ± 0.012 (s=389)	1.167 ± 0.010 (s=384)	-0.2% .. +0.2%
Spherical slab interpolation simple CMS	1.444 ± 0.012 (s=308)	1.442 ± 0.012 (s=318)	-0.3% .. +0.1%
Spherical fault interpolation simple none	1.097 ± 0.009 (s=438)	1.096 ± 0.007 (s=385)	-0.2% .. +0.1%
Cartesian min max surface	2.543 ± 0.016 (s=182)	2.542 ± 0.017 (s=174)	-0.2% .. +0.2%
Spherical min max surface	7.179 ± 0.073 (s=61)	7.182 ± 0.073 (s=67)	-0.6% .. +0.6%

[MFraters]

Thanks!