Switch to upstream `elm-format`

[tfausak]

Blocked by avh4/elm-format#777.

[tfausak]

Here's a summary of where this issue stands today:

• Allow building on Linux ARM64 avh4/elm-format#777: elm-format added support for ARM64.
• avh4/elm-format@231ca84: elm-format upgraded to GHC 9.2.
• avh4/elm-format@85c642d: elm-format upgraded to GHC 9.4.
• elm doesn't compile with any GHC >= 9.2.

It may be possible to get around all this by using elm-tooling.

[tfausak]

I'm closing this issue and archiving this repo. We no longer use this Docker image at ACI Learning. Instead we use a regular Node image with elm-tooling.