Fix hidden command documentation (Issue #1178)

[axaggelpapa30]

This PR corrects an outdated NOTE in the "Hidden Command" documentation page.

The existing documentation states:

NOTE: Defining hidden commands is not supported with annotation based configuration.

However, this statement is no longer accurate. Spring Shell does support the
definition of hidden commands via annotation-based configuration.

For example, the following works as expected:
@command(command = "connect", alias = "c", hidden = true)

This annotation correctly hides the command from:

• the help listing
• the help page for unknown commands
• command completion in interactive mode
• bash completion

The documentation also includes example snippets that demonstrate using
hidden = true, which contradicts the NOTE.

This PR updates the NOTE to reflect the current and correct behavior of the
framework and to avoid confusion for users reading the documentation.

Changes:

• Updated the NOTE block in hidden.adoc
• Clarified that annotation-based hidden commands are supported
• Added accurate wording and an example reference

Closes spring-projects#1178