Remove update checker

git-svn-id: https://plugins.svn.wordpress.org/thumbnail-grid/trunk@982590 b8457f37-d9ea-0310-8a92-e5e31aec5664
Version 3.0.1 Remove update checker

git-svn-id: https://plugins.svn.wordpress.org/thumbnail-grid/trunk@982591 b8457f37-d9ea-0310-8a92-e5e31aec5664