github: submodule actions, take 2

.github/workflows/cmake-single-platform.yml

@@ -20,11 +20,10 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v3
-
-    - name: Update submodules
-      # update/fetch submodules (attached as top-level children of reflect/repo/)
-      run: git submodule update --init --recursive
+    - name: Checkout
+      uses: actions/checkout@v3
+      with:
+        submodules: true
 
     - name: Configure CMake
       # Configure CMake in a 'build' subdirectory. `CMAKE_BUILD_TYPE` is only required if you are using a single-configuration generator such as make.