Update docs/manual/install/index.rst

Co-authored-by: elParaguayo <[email protected]>

docs/manual/install/index.rst

@@ -202,7 +202,7 @@ this rules file changes the group of the relevant files to the ``sudo`` group,
 and changes the file mode to be g+w (i.e. writable by all members of the sudo
 group). The theory here is that most systems qtile is installed on will also
 have the primary user in the ``sudo`` group. However, you can change this to
-whatever you like with the ``-group`` argument; see the sample udev rules.
+whatever you like with the ``--group`` argument; see the sample udev rules.
 
 Note that this file invokes Qtile's hidden ``udev`` from udevd, so udevd will
 need ``qtile`` in its ``$PATH``. For distro packaging this shouldn't be a