OSDOCS-9379#adding IAM permissions

[brendan-daly-red-hat]

Versions: 4.15+

Issue: https://issues.redhat.com/browse/OSDOCS-9379

Link to docs preview: Required GCP permissions for installer-provisioned infrastructure

QE review:

• [x] QE has approved this change.

Additional information:

[ocpdocs-previewbot]

🤖 Fri Nov 29 12:02:34 - Prow CI generated the docs preview:

https://85580--ocpdocs-pr.netlify.app/openshift-enterprise/latest/installing/installing_gcp/installing-gcp-account.html

[brendan-daly-red-hat]

@jianli-wei, PTAL at the draft update.

[jianli-wei]

/label qe-approved

[openshift-ci[bot]]

@brendan-daly-red-hat: all tests passed!

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[brendan-daly-red-hat]

/label peer-review-needed

[brendan-daly-red-hat]

/label merge-review-needed