docs: fix typo on routing page (#10383)

Co-authored-by: David Marr <[email protected]>

Author: marr

documentation/docs/20-core-concepts/10-routing.md

@@ -331,7 +331,7 @@ export async function POST({ request }) {
 
 - `PUT`/`PATCH`/`DELETE`/`OPTIONS` requests are always handled by `+server.js` since they do not apply to pages
 - `GET`/`POST`/`HEAD` requests are treated as page requests if the `accept` header prioritises `text/html` (in other words, it's a browser page request), else they are handled by `+server.js`.
-- Responses to `GET` requests will inlcude a `Vary: Accept` header, so that proxies and browsers cache HTML and JSON responses separately.
+- Responses to `GET` requests will include a `Vary: Accept` header, so that proxies and browsers cache HTML and JSON responses separately.
 
 ## $types