doc: Remove reference to closed SMI metrics support issue (#4566)

#379 is closed hence
removing the reference to the issue from
https://github.com/openservicemesh/osm#smi-specification-support.
Leaving the "In Progress" comment until OSM is added to SMI's metrics
server.

Signed-off-by: mudit singh <mudit.singh@india.nec.com>

README.md

@@ -73,7 +73,7 @@ OSM is under active development and is **NOT** ready for production workloads.
 | TCPRoute | tcproutes.specs.smi-spec.io | [v1alpha4](https://github.com/servicemeshinterface/smi-spec/blob/v0.6.0/apis/traffic-specs/v1alpha4/traffic-specs.md#tcproute) | |
 | UDPRoute | udproutes.specs.smi-spec.io | _not supported_ | |
 | TrafficSplit | trafficsplits.split.smi-spec.io | [v1alpha2](https://github.com/servicemeshinterface/smi-spec/blob/v0.6.0/apis/traffic-split/v1alpha2/traffic-split.md) | |
-| TrafficMetrics  | \*.metrics.smi-spec.io | [v1alpha1](https://github.com/servicemeshinterface/smi-spec/blob/v0.6.0/apis/traffic-metrics/v1alpha1/traffic-metrics.md) | 🚧 **In Progress** [#379](https://github.com/openservicemesh/osm/issues/379) 🚧 |
+| TrafficMetrics  | \*.metrics.smi-spec.io | [v1alpha1](https://github.com/servicemeshinterface/smi-spec/blob/v0.6.0/apis/traffic-metrics/v1alpha1/traffic-metrics.md) | 🚧 **In Progress** 🚧 |
 
 ## OSM Design