[FIX] tour.js: remove synchro between selected property and attribute

This line was previously used to allow attribute selectors to match the
`selected` property, by changing the attribute each time the property
was changed. Now it doesn't make sense since rev c611846 introduced
property selectors + it seems to mess with phantomjs, as the test does
not pass in phantomjs environment but passes ok in a "real" webkit browser.

addons/web/static/src/js/tour.js

@@ -586,7 +586,6 @@ var Tour = {
                 if ($element.is("input") ) {
                     $element.val(step.sampleText);
                 } if ($element.is("select")) {
-                    $element.find("[value='"+step.sampleText+"'], option:contains('"+step.sampleText+"')").attr("selected", true);
                     $element.val(step.sampleText);
                 } else {
                     $element.html(step.sampleText);