Fix bubbles manage button touch target

This change increases the touch area around the manage button, and also uses a dynamic height to scale with the text.

Before: https://screenshot.googleplex.com/9ySstyvcXtqQzwy
After: https://screenshot.googleplex.com/8gdjVkgqHvgosWY

Flag: NONE
Fixes: 308796727
Test: Manual
       - Create and expand bubble
       - Observe manage button height
       - Set font size to large
       - Observe manage button height updated
Change-Id: I610d448e08800864ecc735e7b7a6c230712faffa