Bump android gradle plugin (#372)
Bump android gradle plugin (#372)

Summary:
Pull Request resolved: https://github.com/facebook/flipper/pull/372

Some prep for AndroidX upgrade.

Reviewed By: danielbuechele

Differential Revision: D14101014

fbshipit-source-id: 15571528340ea149be77985b3d194d832f253597

facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper