Update CI to checkout v3

.github/workflows/ci.yml

@@ -20,7 +20,7 @@ jobs:
           - beta
           - nightly
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Install Rust ${{ matrix.rust }}
         uses: actions-rs/toolchain@v1
         with:
@@ -41,5 +41,5 @@ jobs:
     name: Check dependencies
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: EmbarkStudios/cargo-deny-action@v1