doc: fix types in stream doc
Extend return type of read() method with any which is a valid return type for readable streams in object mode.
Checklist
-
documentation is changed or added -
commit message follows commit guidelines
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Extend return type of read() method with any which is a valid return type for readable streams in object mode.