마침 yarn이 알려줘서

warning serverless-appsync-plugin > merge-graphql-schemas@1.7.8: Merge GraphQL Schemas has been deprecated and merged into GraphQL Tools, so it will no longer get updates. Use GraphQL Tools instead to stay up-to-date! Check out <https://www.graphql-tools.com/docs/migration-from-merge-graphql-schemas> for migration and <https://the-guild.dev/blog/graphql-tools-v6> for new changes.