ci: update actions/checkout to v3

Author: EmmanuelP

.github/workflows/linux.yml

@@ -14,7 +14,7 @@ jobs:
   linux:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - name: Install dependencies
       run: |
         pip install meson ninja