kernel-doc/rst: drop redundant unescape in highlighting

This bit is already done by xml_unescape() above.
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

scripts/kernel-doc

@@ -1796,7 +1796,6 @@ sub output_highlight_rst {
 	if ($line eq "") {
 	    print $lineprefix, $blankline;
 	} else {
-	    $line =~ s/\\\\\\/\&/g;
 	    print $lineprefix, $line;
 	}
 	print "\n";