[Bug #1219862] Document correct argument range for pair_content()

Doc/lib/libcurses.tex

@@ -391,7 +391,7 @@ Leave raw mode. Return to normal ``cooked'' mode with line buffering.
 \begin{funcdesc}{pair_content}{pair_number}
 Returns a tuple \code{(\var{fg}, \var{bg})} containing the colors for
 the requested color pair.  The value of \var{pair_number} must be
-between \code{0} and \code{\constant{COLOR_PAIRS} - 1}.
+between \code{1} and \code{\constant{COLOR_PAIRS} - 1}.
 \end{funcdesc}
 
 \begin{funcdesc}{pair_number}{attr}