Change the tipsy gravity for the stripe buttons

- this avoids an issue where the arrow wouldn't point to what we
want when near the edge of the screen
- this avoids an RTL issue where the bubble would go outside of
the screen

Bug: 64258
Change-Id: I1cc9683af2743b093a45b19d7142fe7e5e66423f
Mingle: https://wikimedia.mingle.thoughtworks.com/projects/multimedia/cards/485