Delete linkcheck action

.github/workflows/linkcheck.yml

@@ -1,24 +0,0 @@
-name: linkcheck
-
-on:
-  # Run once per day
-  schedule:
-    - cron: '21 1 * * *'
-
-jobs:
-  build:
-    runs-on: ubuntu-latest
-    steps:
-      # Checkout and setup
-      - name: Checkout
-        uses: actions/checkout@v3
-      - name: Setup
-        uses: actions/setup-node@v3
-        with:
-          node-version: 16
-      # Install and build
-      - name: Install
-        run: npm ci
-      # Run linkcheck, propagate linkcheck failure through grep pipe
-      - name: Linkcheck
-        run: set -o pipefail; npm run linkcheck:prod 2>/dev/null | grep "Getting links from\|BROKEN"