Use lint database from api_version_system

Droidstubs now support using the api-versions.xml from another
droidstubs module, so reuse the one from `api_versions_system`
in `framework-doc-system-stubs`.

Test: m framework-docs-system-stubs
      # Diff stubs before and after
Change-Id: I0aa3a74664e2a9343e90d91b7520ce8bbcadfac5