Remove strange use of $math$ mode to produce a backslash.

Doc/lib/libcgi.tex

@@ -393,7 +393,8 @@ except:
 \end{verbatim}\ecode
 %
 Notes: The assignment to \code{sys.stderr} is needed because the traceback
-prints to \code{sys.stderr}.  The \code{print "$\backslash$n$\backslash$n<PRE>"} statement is necessary to
+prints to \code{sys.stderr}.
+The \code{print "{\e}n{\e}n<PRE>"} statement is necessary to
 disable the word wrapping in HTML.
 
 If you suspect that there may be a problem in importing the traceback

Doc/libcgi.tex

@@ -393,7 +393,8 @@ except:
 \end{verbatim}\ecode
 %
 Notes: The assignment to \code{sys.stderr} is needed because the traceback
-prints to \code{sys.stderr}.  The \code{print "$\backslash$n$\backslash$n<PRE>"} statement is necessary to
+prints to \code{sys.stderr}.
+The \code{print "{\e}n{\e}n<PRE>"} statement is necessary to
 disable the word wrapping in HTML.
 
 If you suspect that there may be a problem in importing the traceback