fix(ci): remove update workflow

Not needed as renovate fulfills this purpose.

.forgejo/workflows/update.yml

@@ -1,71 +0,0 @@
-on:
-  workflow_dispatch:
-  schedule:
-    # 03:42 on Saturdays
-    - cron: '42 3 * * 6'
-env:
-  PR_TITLE: Weekly `cargo update` of dependencies
-  PR_MESSAGE: |
-    Automation to keep dependencies in `Cargo.lock` current.
-
-    The following is the output from `cargo update`:
-  COMMIT_MESSAGE: "chore(deps): cargo update"
-jobs:
-  update-cargo:
-    runs-on: nixos
-    env:
-      BRANCH_NAME: cargo-update
-    steps:
-      - uses: https://git.salame.cl/actions/checkout@v4
-      - run: nix --version
-      - run: nix run .#cargo-update
-      - name: craft PR body and commit message
-        run: |
-          set -xeuo pipefail
-
-          echo "${COMMIT_MESSAGE}" > commit.txt
-          printf '\n\n' >> commit.txt
-          cat cargo_update.log >> commit.txt
-
-          echo "${PR_MESSAGE}" > body.md
-          echo '```txt' >> body.md
-          cat cargo_update.log >> body.md
-          echo '```' >> body.md
-      - name: commit
-        run: |
-          set -xeuo pipefail
-
-          git config user.name forgejo-actions
-          git config user.email forgejo-actions@salame.cl
-          git switch --force-create "$BRANCH_NAME"
-          git add ./Cargo.lock
-          DIFF="$(git diff --staged)"
-          if [[ "$DIFF" == "" ]]; then
-            echo "Cargo.lock was not changed, bailing out and not making a PR"
-            exit 1
-          fi
-          git commit --no-verify --file=commit.txt
-      - name: push
-        run: |
-          set -xeuo pipefail
-          git push --no-verify --force --set-upstream origin "$BRANCH_NAME"
-      - name: open new pull request
-        env:
-          # We have to use a Personal Access Token (PAT) here.
-          # PRs opened from a workflow using the standard `GITHUB_TOKEN` in GitHub Actions
-          # do not automatically trigger more workflows:
-          # https://docs.github.com/en/actions/security-guides/automatic-token-authentication#using-the-github_token-in-a-workflow
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-        run: |
-          set -euo pipefail
-          curl -X POST \
-            -H "Authorization: token $GITHUB_TOKEN" \
-            -H 'Content-Type: application/json' \
-            -d "$(
-              echo '{}' |
-                jq --arg body "$(cat body.md)" \
-                  --arg title "$COMMIT_MESSAGE" \
-                  --arg head "$BRANCH_NAME" \
-                  '{"body": $body, "title": $title, "head": $head, "base": "main"}'
-            )" \
-            "$GITHUB_API_URL/repos/$GITHUB_REPOSITORY/pulls"