Correct Spring Boot dependency version property name used to manage Spring Data

[jxblum]

Spring Boot's version property for all of Spring Data (via the Spring Data BOM) is used to manage the Spring Data module dependencies and versions included and pulled in transitively by Spring Boot.

As of Spring Boot 3.0, the version property for Spring Data changed from spring-data-releasetrain.version to spring-data-bom.version. See here.

Spring Data Commons current documentation refers to the old property, spring-data-releeasetrain.version.

[jxblum]

Verified the docs generation running $ mvn -P distribute install manually from the command-line.

[jxblum]

Apparently, this was already the case back in Spring Boot 2.7.x as well, for instance, in Spring Boot 2.7.7: https://docs.spring.io/spring-boot/docs/2.7.7/reference/html/dependency-versions.html#appendix.dependency-versions.properties