ci: ignore no_default_cases rule and update error handler

- Add no_default_cases to ignored lint rules in analysis_options.yaml
- Remove unnecessary trailing comma in error_handler.dart

Author: fulleni

analysis_options.yaml

@@ -3,6 +3,7 @@ analyzer:
   errors:
     avoid_redundant_argument_values: ignore
     avoid_print: ignore
+    no_default_cases: ignore
   exclude:
     - build/**
 linter:

lib/src/middlewares/error_handler.dart

@@ -85,6 +85,5 @@ String _mapExceptionToCodeString(HtHttpException exception) {
     NetworkException() => 'NETWORK_ERROR',
     UnknownException() => 'UNKNOWN_ERROR',
     _ => 'UNKNOWN_ERROR',
-    
   };
 }