fix: client-secret should only be present when string literal provided for oidc

[hamza-m-masood]

Which problem does the PR fix?

closes: #2727

What's in this PR?

I am fixing the client-secret section in identity configmap. it should render when a string literal is provided and should not render when a k8s secret is provided.

Checklist

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[jessesimpson36]

Seems like a reasonable change to me. do you intend to forward-port / backport it to the other versions, or just 8.5?

[hamza-m-masood]

Thanks @jessesimpson36 I wil make this change to all charts from 8.5 and above.
This change is not necessary for 8.4 since identity exclusively uses env vars

[hamza-m-masood]

I am assuming the integration tests and unit tests for alpha are still broken. I will merge with that assumption