Fix schema

Author: arun-sureshkumar

graphene_federation/service.py

@@ -129,7 +129,7 @@ def get_sdl(schema: Schema) -> str:
         _schema_import.append('"@shareable"')
     if tagged_fields:
         _schema_import.append('"@tag"')
-    _schema = f'extend schema @link(url: "https://specs.apollo.dev/federation/v2.0", import: [{", ".join(_schema_import)}]'
+    _schema = f'schema @link(url: "https://specs.apollo.dev/federation/v2.0", import: [{", ".join(_schema_import)}]'
     _schema += '{ %replace% \n} \n\n'
     _schema_content = ""
     if schema.query: