Fixed ASDoc validation error

Small fix for the following asdoc validation error:

	Text for description in starling.core:Starling/viewPortHeight/get is not valid.
	org.xml.sax.SAXParseException; lineNumber: 10; columnNumber: 54; The element type "p" must be terminated by the matching end-tag "</p>".

	Text for description in starling.core:Starling/viewPortWidth/get is not valid.
	org.xml.sax.SAXParseException; lineNumber: 10; columnNumber: 53; The element type "p" must be terminated by the matching end-tag "</p>".