Allow running Puma Single mode on non-.com envs

What does this MR do?

We want to support running Puma webserver in default/single/non-clustered mode by setting workers: 0, so this validation should be updated.
More at: &5303 (closed)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

N/A

Security

N/A

Related to #300910 (closed)