Typo in idioms/coercion-arguments.md

[horw]

Hello, just small fix in

https://github.com/rust-unofficial/patterns/blob/79467dc4480fd93c85596d4a7bd18160527ce3e2/src/idioms/coercion-arguments.md?plain=1#L38C16-L38C38

vowel_count>=3 should be changed to vowel_count == 3 because reaching 4 is not possible.