update-flake: remove workflow

.gitea/workflows/update-flake.yaml

@@ -1,19 +0,0 @@
-name: update-flake-lock
-on:
-  workflow_dispatch: # allows manual triggering
-  schedule:
-    - cron: '0/2 * * * *' # runs weekly on Sunday at 00:00
-
-jobs:
-  lockfile:
-    runs-on: nix
-    steps:
-      - name: Checkout repository
-        uses: actions/checkout@v3
-      - name: Update flake.lock
-        uses: DeterminateSystems/update-flake-lock@v19
-        with:
-          pr-title: "Update flake.lock" # Title of PR to be created
-          pr-labels: |                  # Labels to be set on the PR
-            dependencies
-            automated