don't add share action to the Shared folder

apps/files/js/fileactions.js

@@ -112,7 +112,7 @@ var FileActions = {
 				addAction(name, action);
 			}
 		});
-		if(actions.Share){
+		if(actions.Share && file !== 'Shared'){
 			addAction('Share', actions.Share);
 		}