fix(rail): Remove unused import

[runkelcorey]

🔔 update Performance Manager Alerts feed to expect new data types

What changes does this PR propose?

Technically, this only removes an import that blocked deployment of 77b9494.

Really, this is to create a checkpoint for 77b9494 and 8d5b028. Those commits:

• coalesced cause_detail and effect_detail with cause_detail.translation and effect_detail.translation, respectively, in Performance Manager
• updated the alerts spec to conform closer to the GTFS spec

How were these changes validated?

1. Updated test_transform_translations to keep the spirit of its tests but change the test mechanics to allow

What questions should reviewers consider?

1. Should the alerts code move out of PM and into Tableau Publisher?

[github-actions]

LCOV of commit 98f523a during Continuous Integration (Python) #1995

Summary coverage rate:
  lines......: 64.7% (3599 of 5561 lines)
  functions..: 29.9% (275 of 920 functions)
  branches...: no data found

Files changed coverage rate: n/a

[huangh]

Should the alerts code move out of PM and into Tableau Publisher?

we would probably want to turn tableau publisher into a long lived ecs task, or alternatively have another tableau-publisher like cron that does all the intermediate conversions, so we can leave tableau publisher as a dumb "publish to tableau" task runner.