docs: add global rate limit to v1.3.0 release notes
Adds global rate limiting to the list of notable
changes for v1.3.0.
## Release v1.3.0
### Notable changes
+- `Rate limiting`: Added capability to perform [global rate limiting](https://release-v1-3.docs.openservicemesh.io/docs/guides/traffic_management/rate_limiting/#configuring-global-rate-limiting) of TCP connections and HTTP requests.
### Breaking changes
- `EgressPolicy` can only be used when global mesh-wide Egress passthrough is disabled. When global passthrough Egress is enabled, EgressPolicy will not be enforced.
