Fix error message typo

Author: adam-fowler

Sources/AWSLambdaEvents/Utils/DateWrappers.swift

@@ -83,7 +83,7 @@ public struct DateTimeCoding: Decodable {
         let dateString = try container.decode(String.self)
         guard let date = Self.dateFormatter.date(from: dateString) else {
             throw DecodingError.dataCorruptedError(in: container, debugDescription:
-                "Expected date to be in iso8601 date format with fractional seconds, but `\(dateString)` does not forfill format")
+                "Expected date to be in date-time format with fractional seconds, but `\(dateString)` does not forfill format")
         }
         self.wrappedValue = date
     }