ci: remove audit because it was useless anyway

It never worked from the start, I've never even run the command locally.

.gitea/workflows/audit.yaml

-name: Security audit
-
-on:
-  schedule:
-    # Runs at 00:00 UTC every sunday
-    - cron: '0 0 * * 0'
-  push:
-    paths:
-      - '**/Cargo.toml'
-      - '**/Cargo.lock'
-  pull_request:
-
-jobs:
-  audit:
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout repository
-        uses: actions/checkout@v3
-      # Ensure that the latest version of Cargo is installed
-      - name: Install Rust
-        uses: https://github.com/dtolnay/rust-toolchain@stable
-      - uses: https://github.com/Swatinem/rust-cache@v2
-      - uses: https://github.com/actions-rs/audit-check@v1
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