Update changelog for v3.12.2 release
## HEAD (Unreleased)
+
+## 3.12.2 (January 5, 2022)
+
- Relax ingress await restrictions (https://github.com/pulumi/pulumi-kubernetes/pull/1832)
- Exclude nil entries from values (https://github.com/pulumi/pulumi-kubernetes/pull/1845)
