Documentation: management-style: Fix formatting of emphsized word

Commit 7f2b3c65

 ("Documentation/ManagementStyle: convert it to ReST
markup") converted _underlined_ to *emphasized* words, but forgot about
an underscore in this case.

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Link: https://lore.kernel.org/r/20200303192113.20761-1-j.neuschaefer@gmx.net


Signed-off-by: Jonathan Corbet <corbet@lwn.net>