Use shared MT setup action fully in dependency baseline workflow

[Copilot]

mt-dependency-update-baseline.yml was still duplicating setup logic that already exists in the shared composite setup action. This PR aligns the workflow with the shared-overwrite convention by relying on MT setup for all duplicated setup behavior.

• Workflow setup alignment

  • Updated .github/workflows/mt-dependency-update-baseline.yml to use:
    • mtransitapps/gh-actions/.github/actions/setup@v1.0.1 (name: MT setup, id: mt-setup)
  • Removed duplicated setup steps now covered by the shared action:
    • submodule checkout and branch switching
    • repository branch switching/pull setup
    • manual MT_GIT_BRANCH env setup step
    • explicit ./commons/code_setup.sh
    • direct tool setup steps:
      • actions/setup-java@v5
      • gradle/actions/setup-gradle@v6
  • Added repo-type env flags required by the shared action’s conditional setup logic:
    • MT_IS_SUBMODULE
    • MT_IS_MAIN_REPO
    • MT_IS_AGENCY_REPO

• Resulting workflow shape

  • The job now delegates setup responsibilities to the shared MT setup action instead of maintaining local duplicates, reducing drift and centralizing setup behavior.

- name: MT setup
  id: mt-setup
  uses: mtransitapps/gh-actions/.github/actions/setup@v1.0.1

[mmathieum]

@copilot https://github.com/mtransitapps/gh-actions/blob/master/.github/actions/setup/action.yml the action does way more, please replace all the steps duplicated here

[Copilot]

Updated in commit 970353a: I removed the duplicated steps (checkout_submodules, submodule branch switching, module branch checkout/pull, MT_GIT_BRANCH setup, and ./commons/code_setup.sh) and now rely on mtransitapps/gh-actions/.github/actions/setup@v1.0.1 for that setup behavior.