Remove adding /odm from GSI makefile

The odm/ is default created under the root directory.
We don't need adding /odm mount pointer now in GSI.

Bug: 77297861
Test: build aosp_arm64_ab-userdebug and boot on a Pixel 2 device.
Change-Id: Ied48439f366acc33595b958b75c2f30d8f6ad57e