remove-user-from-puppet: Remove mention of the training environment
remove-user-from-puppet: Remove mention of the training environment

- The training environment was a spike that no longer exists, and its
  configuration was removed in https://github.com/alphagov/govuk-puppet/pull/10509.

alphagov/govuk-developer-docs,alphagov/govuk-developer-docs,alphagov/govuk-developer-docs,alphagov/govuk-developer-docs