update a description

git-svn-id: https://plugins.svn.wordpress.org/groupdocs-viewer/trunk@791042 b8457f37-d9ea-0310-8a92-e5e31aec5664
Update description

git-svn-id: https://plugins.svn.wordpress.org/groupdocs-viewer/trunk@795159 b8457f37-d9ea-0310-8a92-e5e31aec5664