man: Canonicalize .TH usage

• Use all caps for document title.
• Remove section name as it can be inferred from the section number.
• Name "OpenZFS" as the document source.
• Bump modification date.

While here, fixed trailing whitespace reported by igor.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
Closes #10792