fix(docs): small error (#9868)

* fix(docs): small error

* fix(docs): small typo error

www/apps/book/app/learn/advanced-development/api-routes/validation/page.mdx

@@ -8,7 +8,7 @@ In this chapter, you'll learn how to validate request body parameters in your cu
 
 ## Example Scenario
 
-Consider you're creating a `POST` API route at `/custom`. It accepts two paramters `a` and `b` that are required numbers, and returns their sum.
+Consider you're creating a `POST` API route at `/custom`. It accepts two parameters `a` and `b` that are required numbers, and returns their sum.
 
 The next steps explain how to add validation to this API route, as an example.