Commit 271d3f7a432f ("prometheus service: globalConfig.labels is obsolete") removed globalConfig.labels. Update the test config accordingly.
target_groups was renamed to static_configs in d459916504 ("prometheus service: rename values to match prometheus 1.0 naming."). Catch up.
This is based on @benleys work: https://github.com/NixOS/nixpkgs/pull/8216 I updated changed the user and group ids.