run git submodule manually

.github/workflows/ci.yml

@@ -6,16 +6,16 @@ jobs:
   check:
     runs-on: ubuntu-latest
     steps:
-    - name: Checkout repository and submodules
+    - name: Checkout repository
       uses: actions/checkout@v3
-      with:
-        submodules: true
-        # This is only needed for the flutter submodule.
-        # We can't do a depth-1 clone, because we need the most recent tag
-        # so that Flutter knows its version and sees the constraint in our
-        # pubspec is satisfied.  It's uncommon for flutter/flutter to go
-        # more than 100 commits between tags.  Fetch 1000 for good measure.
-        fetch-depth: 1000
+
+    - name: Checkout flutter submodule
+      # We can't do a depth-1 clone, because we need the most recent tag
+      # so that Flutter knows its version and sees the constraint in our
+      # pubspec is satisfied.  It's uncommon for flutter/flutter to go
+      # more than 100 commits between tags. Fetch 1000 for good measure.
+      run: |
+        git submodule update --init --depth 1000
 
     - name: Add vendored flutter to PATH
       run: |