Documentation: trace: histogram-design: Wrap introductory note in note:: directive

Documentation: trace: histogram-design: Wrap introductory note in note:: directive

Use Sphinx note:: directive for the introductory note at the beginning
of docs, instead of aligned-text paragraph that renders as definition
list.

Reviewed-by: Tom Zanussi <zanussi@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20250916054202.582074-6-bagasdotme@gmail.com>