Use the correct recipe on fuchsia_precache. (flutter#139279)

To run shard tests we need to use flutter_drone recipe.


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.ci.yaml

@@ -678,7 +678,7 @@ targets:
       - .ci.yaml
 
   - name: Linux fuchsia_precache
-    recipe: flutter/flutter
+    recipe: flutter/flutter_drone
     timeout: 60
     properties:
       shard: fuchsia_precache