bump actions to v4 to avoid deprecation

Signed-off-by: Avi Deitcher <avi@deitcher.net>

.github/workflows/publish.yaml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Check out code
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
     - name: Ensure bin/ directory
       run: mkdir -p bin
     - name: Download linuxkit
@@ -45,7 +45,7 @@ jobs:
         sudo ln -s $(pwd)/bin/${{ env.linuxkit_file }} /usr/local/bin/linuxkit
         /usr/local/bin/linuxkit version
     - name: Restore Package Cache
-      uses: actions/cache@v3
+      uses: actions/cache@v4
       with:
         path: ~/.linuxkit/cache/
         key: ${{ runner.os }}-linuxkit-${{ github.sha }}