Use yield from instead of looping yield (#6170)

Author: Kevin Kirsche

requests/models.py

@@ -813,8 +813,7 @@ def generate():
             # Special case for urllib3.
             if hasattr(self.raw, "stream"):
                 try:
-                    for chunk in self.raw.stream(chunk_size, decode_content=True):
-                        yield chunk
+                    yield from self.raw.stream(chunk_size, decode_content=True)
                 except ProtocolError as e:
                     raise ChunkedEncodingError(e)
                 except DecodeError as e: