spring-boot-dependencies contains dependency management for spring-boot-starter-activemq which no longer exists

[yuvanakannan]

Even though the spring-boot-dependencies-3.0.0-M1.pom lists the spring-boot-starter-activemq-3.0.0-M1 as a dependency, spring-boot-starter-activemq-3.0.0-M1 is not available in https://repo.spring.io/milestone.

[bclozel]

Support for ActiveMQ has been removed in #28591. We should remove it's reference from the dependency management.