rhine: remove twrp flags

* These aren't maintained / kept in sync with TWRP.

Change-Id: Ib50cfb0f9c6a5f50af266a25a435d6cbe973aa4a
Inherit HWUI memory limits from frameworks/native

* No need to duplicate it here.

Change-Id: I2ec7e9f09ebefaf7a4ae76b7217919965bf83956