Enable avoid_unnecessary_containers lint (#77294)

diff --git a/analysis_options.yaml b/analysis_options.yaml
index 5eb60fd..05b4cf1 100644
--- a/analysis_options.yaml
+++ b/analysis_options.yaml
@@ -87,7 +87,7 @@
     - avoid_type_to_string
     - avoid_types_as_parameter_names
     # - avoid_types_on_closure_parameters # conflicts with always_specify_types
-    # - avoid_unnecessary_containers # not yet tested
+    - avoid_unnecessary_containers
     - avoid_unused_constructor_parameters
     - avoid_void_async
     # - avoid_web_libraries_in_flutter # not yet tested