replaced method used on model to import the model not the mapping name

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonPydanticV1Codegen.java

@@ -881,7 +881,7 @@ private ModelsMap postProcessModelsMap(ModelsMap objs) {
                     typingImports.add("Union");
                     Set<CodegenDiscriminator.MappedModel> discriminator = model.getDiscriminator().getMappedModels();
                     for (CodegenDiscriminator.MappedModel mappedModel : discriminator) {
-                        postponedModelImports.add(mappedModel.getMappingName());
+                        postponedModelImports.add(mappedModel.getModelName());
                     }
                 }
             }