docs: Typo fix

Change-Id: I2d55747b1226207946f80f04b80b4685e3eea3f9
Signed-off-by: Stephen Finucane <sfinucan@redhat.com>

Author: stephenfin

doc/source/contributor/humaninterfaceguide.rst

@@ -202,7 +202,7 @@ dash (``-``) to an underscore (``_``), and converting to upper case.
   limited set of available short names.
 
 * All long options names shall begin with two dashes (``--``) and use a single dash
-  (``-`` internally between words (``--like-this``).  Underscores (``_``) shall not
+  (``-``) internally between words (``--like-this``).  Underscores (``_``) shall not
   be used in option names.
 
 * Authentication options conform to the common CLI authentication guidelines in