Update checkout action

Author: aDotInTheVoid

.github/workflows/ci.yaml

@@ -19,7 +19,7 @@ jobs:
       matrix:
         rust: [beta, stable, nightly]
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{matrix.rust}}