update error lines for ja examples

Author: davidcarlisle

ja/lesson-15.md

@@ -167,9 +167,9 @@ l.3 \usepackage[leqno}
 
 <script>
   window.addEventListener('load', function(){
-  rlselectline('pre2',3);
-  rlselectline('pre4',3);
-  rlselectline('pre7',3);
-  rlselectline('pre9',7);
+  rlselectline('pre2',4);
+  rlselectline('pre5',4);
+  rlselectline('pre8',4);
+  rlselectline('pre10',8);
   }, false);
 </script>