Cleanup back-compat code for interpreting Run Service status codes

[ericsciple]

No description provided.

[ericsciple]

Tested E2E to make sure everything is still working as expected. Specifically I tested the 422 UnprocessableEntity scenario above. Easy to repro that scenario via reusable workflow with a required secret, with the caller providing an expression that evaluates to empty/nil.

[ericsciple]

name: CI
on:
  workflow_dispatch:
jobs:
  build:
    uses: ./.github/workflows/reuse.yml
    secrets: 
      foo: ${{ github.nosuch }}

# .github/workflows/reuse.yml

on:
  workflow_call:
    secrets:
      foo:
        description: asdf
        required: true
jobs:
  build:
    runs-on: self-hosted
    steps:
      - run: echo hi
        env:
          FOO_SECRET: ${{ secrets.foo }}