README cosmetics

Derive CI status from the "new" Make-based workflow.

(cherry picked from commit 1e2711c)

Author: michaelklishin

README.md

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-[![Test](https://github.com/rabbitmq/rabbitmq-server/actions/workflows/test.yaml/badge.svg)](https://github.com/rabbitmq/rabbitmq-server/actions/workflows/test.yaml)
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 # RabbitMQ Server
 
+[![CI](https://github.com/rabbitmq/rabbitmq-server/actions/workflows/test-make.yaml/badge.svg)](https://github.com/rabbitmq/rabbitmq-server/actions/workflows/test-make.yaml)
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 [RabbitMQ](https://rabbitmq.com) is a [feature rich](https://www.rabbitmq.com/docs),
 multi-protocol messaging and streaming broker. It supports: