chore(ci): subrepo-related cleanup (#18685)

Remove unused workflow. try to revive barretenberg repo mirroring. tweak
stale workflow cleanup

Author: ludamad

.github/workflows/cancel-stale-workflows.yml

@@ -10,8 +10,6 @@ concurrency:
 
 jobs:
   cancel:
-    if: ${{ !github.event.pull_request.merged }}
-
     permissions:
       actions: write
       contents: read
@@ -26,6 +24,7 @@ jobs:
 
     steps:
       - name: Cancel active PR runs for ${{ matrix.workflow_id }}
+        continue-on-error: true
         uses: actions/github-script@5c56fde4671bc2d3592fb0f2c5b5bab9ddae03b1
         with:
           script: |
@@ -51,3 +50,4 @@ jobs:
                 });
               }
             }
+

.github/workflows/mirror-noir-subrepo.yml

@@ -10,6 +10,7 @@ on:
   schedule:
     # Run the workflow every night at 2:00 AM UTC.
     - cron: "0 2 * * *"
+  workflow_dispatch:
 
 jobs:
   mirror-to-barretenberg-repo:
@@ -18,6 +19,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
         with:
+          ref: next
           fetch-depth: 0
           token: ${{ secrets.AZTEC_BOT_GITHUB_TOKEN }}
       - name: Push to barretenberg repo
@@ -27,9 +29,10 @@ jobs:
           git config --global user.email [email protected]
 
           if ./scripts/git_subrepo.sh push $SUBREPO_PATH --branch=master; then
-            git fetch # in case a commit came after this
-            git rebase origin/master
+            git fetch origin next
+            git rebase origin/next
             git commit --amend -m "$(git log -1 --pretty=%B) [skip ci]"
-            git push
+            # We rely on the fixup logic instead
+            # git push origin next
           fi