docs-rst: remove a rst2pdf left over code

The usage of rst2pdf was replaced by pdflatex on a previous
patch. Remove the left-over code at conf.py.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
1 file changed