refactor: remove one-shot workflow: cron/rename-default-branch (#1470)

Change-Id: I1085b7a7bad5eec02da81e131e92abc15af29d2d

.github/workflows/cron.yml

----
-name: cron
-
-on:
-  schedule:
-    - cron: '0 10 31 5 *' # 05/31 at 10:00
-
-permissions:
-  contents: read
-
-jobs:
-  rename-default-branch:
-    runs-on: ubuntu-latest
-    if: github.ref_name == "master"
-    steps:
-      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
-        with:
-          fetch-depth: 0
-
-      - name: configure git remote
-        run: |
-          git remote set-url origin git@github.com:git-bug/git-bug.git
-
-      - name: "merge pull request: 1464"
-        env:
-          GH_TOKEN: ${{ secrets.RENAME_TOKEN_1404 }}
-        run: gh pr merge 1464 --admin --squash
-
-      - name: "set default branch: refs/heads/trunk"
-        env:
-          GH_TOKEN: ${{ secrets.RENAME_TOKEN_1404 }}
-        run: gh repo edit --default-branch trunk
-
-      - name: "set base for all PRs: refs/heads/trunk"
-        env:
-          GH_TOKEN: ${{ secrets.RENAME_TOKEN_1404 }}
-        run: |-
-          for pr in $(gh pr list -B master -s open --json number --jq '.[] | .number'); do
-            gh pr edit "$pr" -B trunk
-          done