Fix javadoc to reference @DefaultMessage instead of @DefaultText.

Fixes issue 7062.

Review-Link: https://gwt-code-reviews.appspot.com/1766803/

Review by: goktug@google.com

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@11469 8db76d5a-ed1c-0410-87a9-c151d255dfc7