Don't inherit updatable_apex from mainline_system

Camera on aosp_* targets are broken because they are inheriting from
updatable_apex.mk through mainline_system.mk. However, the kernels for
the targets on AOSP are too old to support updatable APEX. Temporarily
disabling updatable apex until when the kernels are updated from
internal master.

Bug: 131162245
Test: camera can be captured in aosp_crosshatch
Merged-In: Ibfef74db0769992266ebadf445836d2a183df3f7
Change-Id: Ia0beeb9523ade9bb8180034deb8ef0b01ee1c88b