controller: removes deprecated extproc container port (#1627)

**Description**

Users are advised to use `aigw-admin` port name for aggregating metrics
as per the example:

https://github.com/envoyproxy/ai-gateway/blob/main/examples/monitoring/monitoring.yaml

Signed-off-by: Takeshi Yoneda <[email protected]>

Author: mathetake

internal/controller/gateway_mutator.go

@@ -319,8 +319,6 @@ func (g *gatewayMutator) mutatePod(ctx context.Context, pod *corev1.Pod, gateway
 		ImagePullPolicy: g.extProcImagePullPolicy,
 		Ports: []corev1.ContainerPort{
 			{Name: "aigw-admin", ContainerPort: extProcAdminPort},
-			// TODO: This is for the backward compatibility with v0.3. Remove this after v0.4 is released.
-			{Name: "aigw-metrics", ContainerPort: extProcAdminPort},
 		},
 		Args: g.buildExtProcArgs(filterConfigFullPath, extProcAdminPort, len(mcpRoutes.Items) > 0),
 		Env:  envVars,