Invalid error field name in JSON parser

[maratal]

ARTJsonLikeEncoder tries to parse incoming error in the server's response like this:

NSDictionary *errorReason = [input valueForKey:@"errorReason"];

While in the updated implementation of the server's endpoint it's just an error as stated by Ben here - https://github.com/ably/specification/issues/26

┆Issue is synchronized with this Jira Bug by Unito

[maratal]

See discussion here https://github.com/ably/ably-cocoa/pull/1269