Update upgrading.md
Update upgrading.md

Add short-hand method for shutting down all apps. Useful for users with large number of apps.
dokku/dokku,alexquick/dokku,dokku/dokku,jimjag/dokku,elia/dokku,elia/dokku,fruitl00p/dokku,fruitl00p/dokku,claytonbrown/dokku,progrium/dokku,elia/dokku,claytonbrown/dokku,alexquick/dokku,alexquick/dokku,dokku/dokku,fruitl00p/dokku,alexquick/dokku,progrium/dokku,fruitl00p/dokku,alexquick/dokku,progrium/dokku,fruitl00p/dokku,dokku/dokku,claytonbrown/dokku,claytonbrown/dokku,progrium/dokku,elia/dokku,dokku/dokku,jimjag/dokku,alexquick/dokku,claytonbrown/dokku,jimjag/dokku,jimjag/dokku,elia/dokku,elia/dokku,dokku/dokku,elia/dokku,claytonbrown/dokku,progrium/dokku,elia/dokku,jimjag/dokku,fruitl00p/dokku,alexquick/dokku,fruitl00p/dokku,fruitl00p/dokku,progrium/dokku,claytonbrown/dokku,dokku/dokku,dokku/dokku,jimjag/dokku,jimjag/dokku,alexquick/dokku,jimjag/dokku,progrium/dokku,progrium/dokku,claytonbrown/dokku