Fix typo in Advanced Types.md

Author: shangdrk

pages/Advanced Types.md

@@ -1053,7 +1053,7 @@ As an example of some types that are immediately resolved, we can take a look at
 ```ts
 declare function f<T extends boolean>(x: T): T extends true ? string : number;
 
-// Type is 'string | number
+// Type is 'string | number'
 let x = f(Math.random() < 0.5)
 
 ```