Fix framework-graphics stub jar build rules

The stub jars need to be building against module_current rather than
the mix of SDKs they were building against before. Remove the
sdk_version declarations and start inheriting the defaults which
specifies the correct sdk_version (among other things).

Bug: 144149403
Test: m
Change-Id: If96fab6926f6f46855169189e40503d6c5ab128b