appservice-api: Update changelog
Breaking changes:
* Remove `PartialEq` implementation for `Namespace`
+* Remove `push_events::v1::IncomingRequest::try_into_sync_response` and the
+ `helper` Cargo feature that was gating it
+ * This API is no longer being used by the only known consumer
+ * If you were using it, please let us know!
# 0.6.0
