chore: correct sentence in TypeScript introduction (nodejs#7664)

Author: Uaitt

apps/site/pages/en/learn/typescript/introduction.md

@@ -40,7 +40,7 @@ const justine = {
 const isJustineAnAdult = isAdult(justine);
 ```
 
-The first part (with the `type` keyword) is responsible for declaring our custom object type representing users. Later we utilize this newly created type to create function `isAdult` that accepts one argument of type `User` and returns `boolean`. After this, we create `justine`, our example data that can be used for calling the previously defined function. Finally, we create a new variable with information on whether `justine` is an adult.
+The first part (with the `type` keyword) is responsible for declaring our custom object type representing users. Later we utilize this newly created type to create the function `isAdult` that accepts one argument of type `User` and returns a `boolean`. After this, we create `justine`, our example data that can be used for calling the previously defined function. Finally, we create a new variable with information on whether `justine` is an adult.
 
 There are additional things about this example that you should know. Firstly, if we do not comply with the declared types, TypeScript will inform us that something is wrong and prevent misuse. Secondly, not everything must be typed explicitly—TypeScript infers types for us. For example, the variable `isJustineAnAdult` is of type `boolean` even if we didn't type it explicitly, and `justine` would be a valid argument for our function even though we didn't declare this variable as of `User` type.