Peer-grader line number is offset by 1

[ronxin]

In peer-grader's code viewer, the real Line 1 is displayed as "Line 2". Fixing the location below may work?? Maybe we can move lines 150-154 all on the same line, in order to avoid any unwaned line-breaks inside the pre tag. https://github.com/csev/tsugi/blob/master/mod/peer-grade/peer_util.php#L152