iOS Crashlytics custom key values are inverted

[hichamboushaba]

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When setting custom values for Crashlytics in iOS, the keys and values are inverted. The cause is that we use the wrong order when calling the function here, we pass the key as the first parameter, while it should be the second, as the documentation states too https://firebase.google.com/docs/reference/swift/firebasecrashlytics/api/reference/Classes/Crashlytics#setcustomvalue_:forkey: