Edit: this is no longer applicable with the new iTunes Connect UI, check out Sars’ answer for an updated version
After looking for this page for a few weeks, I finally figured out how to access it:
1) First, go to the Manage Your Apps section on iTunes Connect.
2) Click the app that you want to edit.
3) On the right-hand side of the resulting page, click “Rights and Pricing”:
4) Scroll down and click the terribly-named “Manage iCloud download settings for this app”:
5) A list of all versions of your application will appear. You can check a specific version to prevent it from being downloaded due to “a significant usability issue”:
