Update load test results topic

We currently document the upstream Istio load test results in this module:

modules/ossm-load-test-results.adoc

This module was created against Istio 1.6.8

https://docs.openshift.com/container-platform/4.10/service_mesh/v2x/ossm-performance-scalability.html#ossm-load-test-results_performance-scalability

The current upstream topic documents tests against Istio 1.13.3.

https://istio.io/latest/docs/ops/deployment/performance-and-scalability/

We should update this page to reflect the most recent load tests, as the Envoy numbers have improved.