Update min FRAME_MAX to match that of RabbitMQ 4.1.x

See Breaking Changes and Compatibility Notes in the release notes [1]. Closes #168. 1. https://github.com/rabbitmq/rabbitmq-server/releases/tag/v4.1.0 <!-- This is an auto-generated comment: release notes by coderabbit.ai --> ## Summary by CodeRabbit - **Refactor** - Increased the minimum frame size from 4096 to 8192 for improved data handling. <!-- end of auto-generated comment: release notes by coderabbit.ai -->