Revert "Add aidl::nullable type for nullable in AIDL"

Revert "Use aidl::nullable for nullable type in C++"

Revert submission 10632869-nullable-compat-rvc-dev-plus-aosp

Reason for revert: incorrect merged-in line
Reverted Changes:
I33822bc76:Use aidl::nullable for nullable type in C++
I378dbf848:Add aidl::nullable type for nullable in AIDL

Change-Id: Idcdb59e74d050768aff5f44819a13831c2ce9899

Exempt-From-Owner-Approval: revert wrong submission