rm broken update.yaml (#556)

this pipeline did not work yet, tracked in #65

Reviewed-on: fediversity/fediversity#556

.forgejo/workflows/update.yaml

@@ -1,24 +0,0 @@
-name: update-dependencies
-
-on:
-  workflow_dispatch: # allows manual triggering
-  # FIXME: re-enable when manual run works
-  # schedule:
-  #   - cron: '0 0 1 * *' # monthly
-
-jobs:
-  lockfile:
-    runs-on: native
-    steps:
-      - name: Checkout repository
-        uses: actions/checkout@v4
-      - name: Update pins
-        run: nix-shell --run "npins --verbose update"
-      - name: Create PR
-        uses: https://github.com/KiaraGrouwstra/gitea-create-pull-request@f9f80aa5134bc5c03c38f5aaa95053492885b397
-        with:
-          remote-instance-api-version: v1
-          token: "${{ secrets.DEPLOY_KEY }}"
-          branch: npins-update
-          commit-message: "npins: update sources"
-          title: "npins: update sources"