Predicate to reject an expiration time claim value equal to or before the current time

Example

iex> seconds = DateTime.to_unix(DateTime.utc_now) + 1
...> Exp.reject?(seconds, %{})
false

Returns true if the current time is after numeric_date; otherwise returns false

numeric_date is the number of seconds from the Unix Epoch (1970-01-01T00:00:00Z UTC) until the specified UTC date/time; non-integer values may be used