Replace a random number with an unreachable `fatalError`  (#1148)
Replace a random number with an unreachable `fatalError`  (#1148)

After [this review comment ](https://github.com/RevenueCat/purchases-ios/pull/1124#discussion_r781401934)

> Feel free to do this in another PR, but to document that I would replace it with `fatalError("Unreachable")`

Tiny PR to replace a random number with a `fatalError` in an unreachable return sentence.
RevenueCat/purchases-ios,RevenueCat/purchases-ios,RevenueCat/purchases-ios,RevenueCat/purchases-ios,RevenueCat/purchases-ios