Workaround: delete the app from your iTunes library first, then download the 'clean' version of 2.0 rather than the update.
[edit] Direct Link: https://itunes.apple.com/app/gmail/id422689480
[edit] Direct Link: https://itunes.apple.com/app/gmail/id422689480
Edit: tried the link above and still get the same error (and I've never installed it before, so this should be a fresh install).