Update certificate tool tip in webhooks and doc to clarify use case

[robotdan]

Update certificate tool tip in webhooks and doc to clarify use case

Description

• Update Webhook settings UI for Certificate to clarify what this is and what it is not.
• This is not mutual TLS, it is just a trusted certificate.
• The use case for this field is to use a self-signed cert, or any cert that the JDK doesn't come with the root CA to verify the trust chain.
• Review the API doc as well to clarify the usage and what this value does.
• Currently it says this is a client certificate which I believe is an incorrect description.

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