Modify RabbitMQ credentials in test templates to comply with rabbitmq.env

[jbrada]

When running the integration tests, it fails to connect to RabbitMQ because the pre-made integration tests configuration templates contain different RabbitMQ login credentials than are in rabbitmq.env.

This pull request modifies the templates to contain the same values as the default rabbitmq.env values

[what-the-diff[bot]]

PR Summary

• AMQP credentials updated The amqp-user and amqp-password have been changed from 'guest' to 'magento' to improve security.
• Applied to Magento Commerce Cloud versions These changes have been made in the install config files for both 2.3 and 2.4 versions of Magento Commerce Cloud (MCC).

[markshust]

Thanks so much for this update @jbrada and for the approval @piotrkwiecinski! I've been down a bit of a wormhole this year but am making my way back to this project to get some updates in.

Merging this in 👍