Wikipedia's article first sentence is "A prime number (or a prime) is a natural number...". This excludes de facto negative integers. In the paragraph you mention: " The integers are a ring, and the prime numbers in the integers have been generalized to rings in two different ways,.." This is a generalization of prime numbers, and doesn't affect the definition of what is a prime number. Moreover, if anyone would have a doubt, the description clearly explains what must be considered a prime number in this kata. Removing the kata for this would just be ridiculous.