Remove regex constraints. Only allow functions

[CathalMullan]

Can bring your own regex if you want.

[codspeed-hq[bot]]

CodSpeed Performance Report

Merging #86 will improve performances by 3.58%

_{Comparing 85-simplify-constraints (331c424) with main (4f572f6)}

Summary

⚡ 1 improvements ✅ 21 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	85-simplify-constraints	Change
⚡	wayfind	40.9 µs	39.5 µs	+3.58%