docs: use canonical loop in streaming concepts (#7131)

docs/core_docs/docs/concepts/streaming.mdx

@@ -59,7 +59,7 @@ The type of chunk yielded by the `stream()` methods depends on the component bei
 The `stream()` method returns an iterator that yields these chunks as they are produced. For example,
 
 ```typescript
-for await (const chunk in await component.stream(someInput)) {
+for await (const chunk of await component.stream(someInput)) {
     // IMPORTANT: Keep the processing of each chunk as efficient as possible.
     // While you're processing the current chunk, the upstream component is
     // waiting to produce the next one. For example, if working with LangGraph,