[OSDOCS-11239]:Update OSD on GCP CSS Prereqs to include changes needed as part of WIF

[mletalie]

Version(s):

4.16+ Issue:

https://issues.redhat.com/browse/OSDOCS-11239 Link to docs preview:

QE review:

• [ ] QE has approved this change.

Additional information:

[ocpdocs-previewbot]

🤖 Fri Jul 05 13:19:13 - Prow CI generated the docs preview:

https://78457--ocpdocs-pr.netlify.app/openshift-dedicated/latest/osd_planning/gcp-ccs.html

[openshift-ci[bot]]

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