Update changelog for v3.4.0 release
## HEAD (Unreleased)
+## 3.4.0 (June 17, 2021)
+
- Add skipAwait option to helm.v3 SDKs. (https://github.com/pulumi/pulumi-kubernetes/pull/1603)
- Add skipAwait option to YAML SDKs. (https://github.com/pulumi/pulumi-kubernetes/pull/1610)
- [sdk/go] `ConfigGroup` now respects explicit provider instances when parsing YAML. (https://github.com/pulumi/pulumi-kubernetes/pull/1601)
