try this
listitems_markup = '<li class="nomarigin"><img src="' + itemThumbnail + '"">
<div class="myParagraph"><p>You viewed ' + itemName + '</p><p>You spent '+itemTimeSpent+' on this activity</p><p>You '+itemRating+' this item</p></div><p class="ui-li-aside">'+itemViewedTime+'</p></li>';
in css
.nomarigin {margin-bottom:0 !important;}