update: require that unmarshaller used to create a Receiver is Send (#702)

* update: require that unmarshaller used to create a Receiver is Send

* update: changelogs

* Fix typo in CHANGELOG.md

Co-authored-by: John DiSanti <jdisanti@amazon.com>

* Fix typo in aws/SDK_CHANGELOG.md

Co-authored-by: John DiSanti <jdisanti@amazon.com>

* add: test ensuring Receiver is Send

* remove: extra colons