ci: update checkout to v3

.github/workflows/check.yml

@@ -34,7 +34,7 @@ jobs:
         run: pacman -Syu git rust clang gcc libarchive pkgconf --noconfirm --needed
 
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Format
         run: cargo fmt -- --check