fix a bookinfo example setting for extensionProviders

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[istio-testing]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: incfly, t-matsuo

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Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/istio-ecosystem/authservice/blob/master/OWNERS)~~ [incfly] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[incfly]

can you try to fix CLA?

[t-matsuo]

can you try to fix CLA?

Sorry, I close this PR.