vndk.go: remove keymint

keymint-unstable is the VNDK variant (and this list is only checked to
be a superset of the desired libraries).

The other library exists, but it is removed because it's not in the VNDK
and this list is only for VNDK libs.

Bug: 173660792
Test: build
Change-Id: I0e1a2a7af13f132cd3bfa4ca1305c098acbe747b