Revert "Make twrp.fstab buildable"

This reverts commit 14b47bd0f5f74c58678539f95749e0208b147412.

Move away from a buildable fstab for TWRP, as it does not provide an
override mechanism that fits our use case. Instead we rely on
PRODUCT_COPY_FILES in the device configurations for the different build
variants.

Issue: FP2N-325
Change-Id: I570be47cc40aac683f455dbf0fba4069ae751200
1 file changed