ci: use actions/checkout@v3

Author: astratagem

.github/workflows/check.yml

@@ -11,7 +11,7 @@ jobs:
   check:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2.4.0
+    - uses: actions/checkout@v3
       with:
         submodules: true
         fetch-depth: 0