set fetch depth 1000 to let flutter know what version it is on

.github/workflows/ci.yml

@@ -10,6 +10,12 @@ jobs:
       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: Add vendored flutter to PATH
       run: |