scroll: replace absolute import with relative one

Fixing this will be useful when we'll want to get rid of require-kernel.

This was introduced by f1fcd16894 ("Add settings to scroll on edition out of
viewport") in 2018-01-03.

src/static/js/scroll.js

@@ -5,7 +5,7 @@
   Browser Line = each vertical line. A <div> can be break into more than one
   browser line.
 */
-var caretPosition = require('/caretPosition');
+var caretPosition = require('./caretPosition');
 
 function Scroll(outerWin) {
   // scroll settings