Update elements.rst

Fixed a typo in the $lineStyle example (defined previously as $linestyle but used as $lineStyle)

docs/elements.rst

@@ -414,7 +414,7 @@ Line elements can be added to sections by using ``addLine``.
 
 .. code-block:: php
 
-    $linestyle = array('weight' => 1, 'width' => 100, 'height' => 0, 'color' => 635552);
+    $lineStyle = array('weight' => 1, 'width' => 100, 'height' => 0, 'color' => 635552);
     $section->addLine($lineStyle)
 
 Available line style attributes: