fix duplicate string (#18233)

Author: vicb

src/content/docs/workers/reference/how-the-cache-works.mdx

@@ -35,7 +35,7 @@ The Cache API is not compatible with tiered caching. To take advantage of tiered
 
 When using single-file purge to purge assets cached by a Worker, make sure not to purge the end user URL. Instead, purge the URL that is in the `fetch` request. For example, you have a Worker that runs on `https://example.com/hello` and this Worker makes a `fetch` request to `https://notexample.com/hello`.
 
-As far as cache is concerned, the asset in the `fetch` request (`https://notexample.com/hello`) is the asset that is cached (`https://notexample.com/hello`). To purge it, you need to purge `https://notexample.com/hello`.
+As far as cache is concerned, the asset in the `fetch` request (`https://notexample.com/hello`) is the asset that is cached. To purge it, you need to purge `https://notexample.com/hello`.
 
 Purging the end user URL, `https://example.com/hello`, will not work because that is not the URL that cache sees. You need to confirm in your Worker which URL you are actually fetching, so you can purge the correct asset.