Fix update_current.py

I3baf5b22f800f35db5517c66f84e7b9c11b101c5 passed a build_id object
instead of a string to fetch_artifact for core.current.stubs.jar,
which then attempted to fetch from a build called
'<__main__.buildId object at 0x7fbdfaf0c518>'.  Pass build_id.fs_id
instead.

Bug: 72206056
Test: ./update_current.py -p 4603536
Change-Id: Ieba4b66455477b8edbf16595a55e0812fca76eac
1 file changed