RFR(JDK12/JAXP/java.xml) 8194680: StartElement#getAttributes and getNamespaces refer to incorrect package

[Joe Wang]

Hi,

Please review a javadoc fix for a couple of incorrect references to the 
javax.xml.stream package. Attribute and Namespace are both in the 
javax.xml.stream.events, and so is StartElement where they are referenced.

JBS: https://bugs.openjdk.java.net/browse/JDK-8194680
webrevs: http://cr.openjdk.java.net/~joehw/jdk12/8194680/webrev/

Thanks,
Joe