Update changelog for v3.8.3 release
## HEAD (Unreleased)
+## 3.8.3 (October 29, 2021)
+
- Add env variable lookup for k8s client settings (https://github.com/pulumi/pulumi-kubernetes/pull/1777)
- Fix diff logic for CRD kinds with the same name as a built-in (https://github.com/pulumi/pulumi-kubernetes/pull/1779)
