Fix gcloud config syntax for e2e test setup

[JeromeJu]

Changes

This commit fixes the argument passed in the gcloud key creation command.

Thanks @XinruZhang for spotting this.

Submitter Checklist

As the author of this PR, please check off the items in this checklist:
/kind bug

• [n/a] Has Docs included if any changes are user facing
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Release Notes

NONE

[afrittoli]

/kind documentation

[afrittoli]

Thank you, nice catch!
/approve

[jerop]

/lgtm

[tekton-robot]

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