Upgrade DRUID_DOCS_VERSION from 0.20.0 to latest version

[asdf2014]

Description

Upgrading the value of DRUID_DOCS_VERSION const from 0.20.0 to latest version.

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This PR has:

• [x] been self-reviewed.
  • [x] using the concurrency checklist (Remove this item if the PR doesn't have any relation to concurrency.)
• [x] added documentation for new or modified features or behaviors.
• [x] added Javadocs for most classes and all non-trivial methods. Linked related entities via Javadoc links.
• [x] added or updated version, license, or notice information in licenses.yaml
• [x] added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• [x] added unit tests or modified existing tests to cover new code paths, ensuring the threshold for code coverage is met.
• [x] added integration tests.
• [x] been tested in a test Druid cluster.