Fix resource codegen unit test (#317)

Co-authored-by: Roja Reddy Sareddy <rsareddy@amazon.com>

Author: rsareddy0329

tst/tools/test_resources_codegen.py

@@ -1253,7 +1253,7 @@ def test_get_node(self):
 @Base.add_validate_call
 def get_node(
     self,
-    node_id: str,
+    node_id: Optional[str] = Unassigned(),
     session: Optional[Session] = None,
     region: Optional[str] = None,
 ) -> Optional[shapes.ClusterNodeDetails]: