PRODUCT_PRODUCT_VNDK_VERSION is set to 'current' by default. Now, we
can generate product variants without checking the
PRODUCT_PRODUCT_VNDK_VERSION build variable. Remove reading the
PRODUCT_PRODUCT_VNDK_VERSION variable from soong and generate product
variants by default.
Bug: 302255959
Test: m
Change-Id: I9a9b2076f4367c5ce9a393bbb206f8dee3884bd8