Override POD Cidr for 500 node cluster

For large clusters or environments, the default Pod CIDR
is not sufficient.

We added POD_CIDR var in #69635

Author: Sandeepyadav93

ci-operator/config/openshift-eng/ocp-qe-perfscale-ci/openshift-eng-ocp-qe-perfscale-ci-main__rosa_hcp-4.20-candidate-x86-loaded-upgrade-from-4.19.yaml

@@ -162,6 +162,7 @@ tests:
       NP_MAX_UNAVAILABLE: 25%
       OCM_LOGIN_ENV: staging
       OPENSHIFT_VERSION: 4.19.9
+      POD_CIDR: "10.128.0.0/10"
       PPROF: "false"
       READY_WAIT_TIMEOUT: 30m
       REGION: us-west-2