Use :nodoc: to limit public API [ci skip]

[MSP-Greg]

Description

Use :nodoc: and add a comment that isn't parsed (note the two blank lines after it) to the following classes/modules:

• Client
• Cluster::Worker
• Cluster::WorkerHandle
• Request

The comment is added to clarify the API status, especially if people are unfamiliar with :nodoc:.

Some classes/modules really shouldn't be part of the public API, as changes to the public API should only be done with major version updates.

A super top secret, double overtime folder exists at https://msp-greg.github.io/puma_test/ which shows how these changes would appear in docs.

Comments? Add more classes/modules?

Your checklist for this pull request

• I have reviewed the guidelines for contributing to this repository.
• I have added (or updated) appropriate tests if this PR fixes a bug or adds a feature.
• My pull request is 100 lines added/removed or less so that it can be easily reviewed.
• If this PR doesn't need tests (docs change), I added [ci skip] to the title of the PR.
• If this closes any issues, I have added "Closes #issue" to the PR description or my commit messages.
• I have updated the documentation accordingly.
• All new and existing tests passed, including Rubocop.

[dentarg]

👍