Fix typo in custom-hooks.mdx
Removed duplicated `as as`
@@ -40,7 +40,7 @@ instead of copying the code, we can move the logic into a custom hook.
We'll start by creating a new function called `use_event`.
The `use_` prefix denotes that a function is a hook.
This function will take an event target, an event type and a callback.
-All hooks must be marked by `#[hook]` to function as as hook.
+All hooks must be marked by `#[hook]` to function as hook.
```rust
use web_sys::{Event, EventTarget};
