"The capability fags" should be "The capability flags".

In rst markup, a incorrect markup expression is causing bad rendering in
Sphinx output. Replace the erroneous single quote by a backquote.
Signed-off-by: NRemi Andruccioli <remi.andruccioli@gmail.com>
Link: https://lore.kernel.org/r/20200808163123.17643-1-remi.andruccioli@gmail.comSigned-off-by: NJonathan Corbet <corbet@lwn.net>