Re-enable backporting to v3-4-test for the 3.4.0 RC phase (#74798)

The beta fast-forward phase is over: v3-4-test now diverges from main and takes changes only by cherry-picking, so the backport automation that was paused for the betas has to come back on, otherwise contributors' backport-to-v3-4-test labels silently do nothing.

Dependabot and the scheduled upgrade check stay paused during the RC phase to avoid dependency and CI churn on the release branch.

.github/boring-cyborg.yml

@@ -373,26 +373,23 @@ labelPRBasedOnFilePath:
     - .rat-excludes
     - .readthedocs.yml
 
-  # Paused while v3-4-test is fast-forwarded to main for the 3.4.0 betas - nothing is
-  # cherry-picked yet. Uncomment when the 3.4.0 RCs start (see "Beta releases" in
-  # dev/README_RELEASE_AIRFLOW.md).
   # This should be copy of the "area:dev-tools" above minus contributing docs and some files that should
   # only make sense in main - it should be updated when we switch maintenance branch.
   # Scoped to PRs targeting `main` only — a PR opened directly against v3-4-test
   # does not need a backport-to-v3-4-test label.
-  # backport-to-v3-4-test:
-  #   paths:
-  #     - scripts/**/*
-  #     - dev/**/*
-  #     - .github/**/*
-  #     - Dockerfile.ci
-  #     - yamllint-config.yml
-  #     - .dockerignore
-  #     - .hadolint.yaml
-  #     - .pre-commit-config.yaml
-  #     - .rat-excludes
-  #   targetBranchFilter:
-  #     - ^main$
+  backport-to-v3-4-test:
+    paths:
+      - scripts/**/*
+      - dev/**/*
+      - .github/**/*
+      - Dockerfile.ci
+      - yamllint-config.yml
+      - .dockerignore
+      - .hadolint.yaml
+      - .pre-commit-config.yaml
+      - .rat-excludes
+    targetBranchFilter:
+      - ^main$
 
   # Apply to PRs touching airflow-ctl code so the release manager notices when a
   # fix should land on the airflow-ctl/v0-1-test maintenance branch.

.github/workflows/automatic-backport.yml

@@ -51,7 +51,7 @@ jobs:
           # Branches fast-forwarded to main during a beta phase - a backport PR there would make
           # them diverge from main. Empty this list when the RCs start (see "Beta releases"
           # in dev/README_RELEASE_AIRFLOW.md).
-          BACKPORT_PAUSED_BRANCHES: '["v3-4-test"]'
+          BACKPORT_PAUSED_BRANCHES: '[]'
         with:
           script: |
             const pausedBranches = JSON.parse(process.env.BACKPORT_PAUSED_BRANCHES);