ci: add checkout step

.gitea/workflows/ci.yaml

@@ -6,17 +6,11 @@ on:
       - main
 
 jobs:
-  env:
-    runs-on: linux
-    steps:
-      - name: Show env
-        run: env | sort
-
   build:
     runs-on: linux
     steps:
-      - name: List files
-        run: ls -alh
+      - name: Checkout
+        uses: actions/checkout@v4
       - name: Build tarball
         run: make tarball
       - name: Build rpm package