[media] index.rst: Fix LaTeX error in interactive mode on Sphinx 1.4.x

[media] index.rst: Fix LaTeX error in interactive mode on Sphinx 1.4.x

The Sphinx 1.4.x definition for \DUrole is:

\providecommand*{\DUrole}[2]{%
  \ifcsname DUrole#1\endcsname%
    \csname DUrole#1\endcsname{#2}%
  \else% backwards compatibility: try \docutilsrole#1{#2}
    \ifcsname docutilsrole#1\endcsname%
      \csname docutilsrole#1\endcsname{#2}%
    \else%
      #2%
    \fi%
  \fi%
}

This is broken when it is used inside a \begin{alltt} block.
So, replace it by just "#2", as this won't cause troubles, and
it is one of the fallback methods for it.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>