media: Fix building pdfdocs

Commit 8d0e3fc6 ("media: Add 2-10-10-10 RGB formats") added
documentation for a few new RGB formats. The table has column-width
specifiers for 34 columns used in pdfdocs build.

However, the new table has a couple of rows with 35 columns which
confused Sphinx's latex builder. The resulting .tex file causes
an error in a later stage of a pdfdocs build.

Remove the trailing empty dash lines to fix the issue.

Fixes: 8d0e3fc6 ("media: Add 2-10-10-10 RGB formats")
Reported-by: Akira Yokosawa <akiyks@gmail.com>
Link: https://lore.kernel.org/r/12250823-8445-5854-dfb8-b92c0ff0851e@gmail.com/Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Tested-by: Akira Yokosawa <akiyks@gmail.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Mauro Carvalho Chehab <mchehab@kernel.org>
  [akiyks: explain the cause of build error]
Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Link: https://lore.kernel.org/r/29380b3e-1daa-3aef-1749-dbd9960ba620@gmail.comSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/userspace-api/media/v4l/pixfmt-rgb.rst

@@ -868,7 +868,6 @@ number of bits for each component.
       - r\ :sub:`4`
       - r\ :sub:`3`
       - r\ :sub:`2`
-      -
     * .. _V4L2-PIX-FMT-RGBA1010102:
 
       - ``V4L2_PIX_FMT_RGBA1010102``
@@ -909,7 +908,6 @@ number of bits for each component.
       - r\ :sub:`4`
       - r\ :sub:`3`
       - r\ :sub:`2`
-      -
     * .. _V4L2-PIX-FMT-ARGB2101010:
 
       - ``V4L2_PIX_FMT_ARGB2101010``
@@ -950,7 +948,6 @@ number of bits for each component.
       - r\ :sub:`6`
       - r\ :sub:`5`
       - r\ :sub:`4`
-      -
 
 .. raw:: latex