Group keys broken

[mhornbacher]

a blank env key gets appended to the group keys, causing the YAML to be invalid

Here is our output generated by the plugin:

Which generates the following error:

2022-09-22 19:56:58 WARN   POST https://agent.buildkite.com/v3/jobs/018366c6-14b4-4e2e-95e5-08817c16d4ee/pipelines: 422 `env` is not a valid property on a step group. Please check the documentation to get a full list of supported properties. (Attempt 1/60 Retrying in 5s)
--
  | 2022-09-22 19:56:58 ERROR  Unrecoverable error, skipping retries
  | 2022-09-22 19:56:58 FATAL  Failed to upload and process pipeline: POST https://agent.buildkite.com/v3/jobs/018366c6-14b4-4e2e-95e5-08817c16d4ee/pipelines: 422 `env` is not a valid property on a step group. Please check the documentation to get a full list of supported properties.
  | 🚨 Error: The command exited with status 1