[chore](auth) Fix mislabeled log strings and remove debug main in authorization plugin path

[arpitjain099]

What problem does this PR solve?

Small tidy-ups I noticed while reading through the authorization plugin path (AccessControllerManager and the Ranger controller) for the OpenFGA work.

Two things:

• In AccessControllerManager.loadAccessControllerPlugins() the two log/exception strings for the classpath loader say "Authentication Plugin Factories", but this method loads AccessControllerFactory instances (authorization). The directory loader a few lines down already logs "Access Controller Plugin Factory", so this just makes the classpath branch consistent and stops the messages from pointing a reader at the wrong subsystem. The class javadoc also called the manager the entry point of "privilege authentication"; corrected to "authorization".
• RangerDorisAccessController still carries a leftover public static void main marked "For test only" that constructs a controller and prints to stdout. It is dead code (nothing references it, and it is not a real test) so I removed it.

No behavior change, log wording and a dead method only.

Release note

None

Check List (For Author)

• Test

  • No need to test or manual test. Explain why:
    • This is a refactor/code format and no logic has been changed.

• Behavior changed:

  • No.

• Does this need documentation?

  • No.

I'll keep looking at where I can help Doris support different authentication and authorization systems as I go.

[hello-stephen]

Thank you for your contribution to Apache Doris.
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