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
diff --git a/update_current.py b/update_current.py
index 0f86319..2820192 100755
--- a/update_current.py
+++ b/update_current.py
@@ -265,7 +265,7 @@
         # Unclear if this is actually necessary.
         extract_to(zipFile, paths, 'framework.aidl', system_path)
 
-    artifact_path = fetch_artifact(target, build_id, 'core.current.stubs.jar')
+    artifact_path = fetch_artifact(target, build_id.fs_id, 'core.current.stubs.jar')
     if not artifact_path:
         return False