Fix: Syntax error in the code example for trace_generator_functions documentation (#755)

Issue description as below:
#754

Co-authored-by: Ruyi Chiang <[email protected]>
Co-authored-by: William FH <[email protected]>

Author: 3 people

docs/observability/how_to_guides/trace_generator_functions.mdx

@@ -28,7 +28,7 @@ for output in my_generator():
 import asyncio\n
 @traceable
 async def my_async_generator():
-    hunk in ["Hello", "World", "!"]:
+    for chunk in ["Hello", "World", "!"]:
         yield chunk\n
 # Stream to the user
 async def main():