Fix swapped enum name mistake

ok() converts Result to Option and not the other way around

README.md

@@ -6176,7 +6176,7 @@ fn main() {
 
 This prints `["Unknown", "Doug Suttles"]`.
 
-Since `.filter_map()` needs an `Option`, what about `Result`? No problem: there is a method called `.ok()` that turns `Option` into `Result`. It is called `.ok()` because all it can send is the `Ok` result (the `Err` information is gone). You remember that `Option` is `Option<T>` while `Result` is `Result<T, E>` with information for both `Ok` and `Err`. So when you use `.ok()`, any `Err` information is lost and it becomes `None`.
+Since `.filter_map()` needs an `Option`, what about `Result`? No problem: there is a method called `.ok()` that turns `Result` into `Option`. It is called `.ok()` because all it can send is the `Ok` result (the `Err` information is gone). You remember that `Option` is `Option<T>` while `Result` is `Result<T, E>` with information for both `Ok` and `Err`. So when you use `.ok()`, any `Err` information is lost and it becomes `None`.
 
 Using `.parse()` is an easy example for this, where we try to parse some user input. `.parse()` here takes a `&str` and tries to turn it into an `f32`. It returns a `Result`, but we are using `filter_map()` so we just throw out the errors. Anything that is `Err` becomes `None` and is filtered out by `.filter_map()`.