Lint: Treat trailing comma voilation as error

analysis_options.yaml

@@ -40,7 +40,7 @@ analyzer:
     exhaustive_cases: error
     curly_braces_in_flow_control_structures: error
     directives_ordering: error
-    require_trailing_commas: warning
+    require_trailing_commas: error
     always_use_package_imports: warning
     prefer_final_fields: error
     unused_import: error