Remove security audit workflow for now

.github/workflows/audit.yml

@@ -1,18 +0,0 @@
-name: Security audit
-on:
-  pull_request:
-    paths: Cargo.lock
-  schedule:
-    - cron: '0 0 * * *'
-jobs:
-  security_audit:
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout sources
-        uses: actions/checkout@v1
-        with:
-          fetch-depth: 50
-      - name: Run cargo audit
-        uses: actions-rs/audit-check@v1
-        with:
-          token: ${{ secrets.GITHUB_TOKEN }}