Remove jitsu authentication

What does this MR do and why?

Since Jitsu initialization is removed, JitsuAuthentication is not used anymore. This MR removes JitsuAuthentication as part of Jitsu cleanup.

From GitLab LLM Bot:

This merge request removes the Jitsu authentication feature from the codebase. It removes the JitsuAuthentication class and its associated tests. The code changes involve removing API calls to Jitsu for generating access tokens, creating API keys, and creating ClickHouse destinations. The merge request also removes the necessary configurations and settings related to Jitsu authentication.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #406659 (closed)