Documentation: fbcon: Reindent 8th step of attach/detach/unload

Properly indent 8th step text (as enumerated list item) to be inline
with other steps.

Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20250909063744.30053-3-bagasdotme@gmail.com>