doc: btrace: fix wrong format on doc

The synopsis part of the btrace documentation gets highlighted with
wrong format. Let's fix the format. There is no change to the contents.

Signed-off-by: Fukui Daichi <a.dog.will.talk@akane.waseda.jp>
Link: https://lore.kernel.org/r/20240117083651.954-1-a.dog.will.talk@akane.waseda.jp
Signed-off-by: Jens Axboe <axboe@kernel.dk>
1 file changed