123197896: The last-released API file is the wrong one

Fix the sorting of signature files.

Bug: 123197896
Test: Manual: Verified that the contents of
out/soong/.intermediates/prebuilts/sdk/last-released-public-api/gen/last-released-api.txt
is the same as 28/public/api/android.txt (after deleting 29/*, done
separately)

Change-Id: I08b90bffe423c484dda11421d69b7c669124dbca
1 file changed