Fix: cargo-audit installation issue in workflow

Author: ignorant05

.github/workflows/ci.yml

@@ -40,7 +40,10 @@ jobs:
           restore-keys: ${{ runner.os }}-cargo-
 
       - name: Install cargo-audit
-        run: cargo install cargo-audit --locked
+        run: |
+          if ! command -v cargo-audit &> /dev/null; then
+            cargo install cargo-audit --locked
+          fi
 
       - name: fmt
         run: cargo fmt --all -- --check