By default createURLAnnotation will create a cell with a solid border around it.  This is controlled by the haruAnnotation object returned by the method.  Create a reference to the haruAnnotation object and alter the border style to remove the solid border.
<?php
$haruAnotation = $currentHaruPage->createURLAnnotation(Array($leftX,$bottomY,$rightX,$topY),'http://'.$dataItem);
$haruAnotation->setBorderStyle(0, 0, 0); // this alters the border
?>
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