release-notes: add rate limiting to v1.2 notes
Adds rate limiting to the v1.2 release notes.
- Along with root certificate rotation we support custom trust domains, as well as rotating to new trust domains with no downtime.
- Envoy has been updated to v1.22 and uses the `envoyproxy/envoy-distroless` image instead of the deprecated `envoyproxy/envoy-alpine` image.
- Added support for Kubernetes 1.23 and 1.24
+- `Rate limiting`: Added capability to perform local per-instance [rate limiting of TCP connections and HTTP requests](https://release-v1-2.docs.openservicemesh.io/docs/guides/traffic_management/rate_limiting).
### Breaking Changes
