[DOC][Breaking Change] Deprecate setting certificate_content with certificate in Data Prepper

[chenqi0805]

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Tell us about your request. Provide a summary of the request and all versions that are affected.
Data Prepper will start to deprecate certificate_content setting keyword with certificate which could be either the public key content or the file path.

What other resources are available? Provide links to related issues, POCs, steps for testing, etc.