docs-rst: add package adjustbox

We need adjustbox to allow adjusting the size of tables that
are bigger than the line width. There are quite a few of them
at the media books.
Signed-off-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Documentation/conf.py

@@ -326,6 +326,9 @@ latex_elements = {
         \\setromanfont{DejaVu Sans}
         \\setmonofont{DejaVu Sans Mono}
 
+	% To allow adjusting table sizes
+	\\usepackage{adjustbox}
+
      '''
 }