CI: use checkout v3

Signed-off-by: Akihiro Suda <[email protected]>

Author: AkihiroSuda

.github/workflows/test.yml

@@ -16,7 +16,7 @@ jobs:
     runs-on: ${{ matrix.platform }}
     timeout-minutes: 40
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
         with:
           fetch-depth: 1
       - name: Show host info