[Docs] Missing Spring Boot compatibility guide for Spring Cloud 2021 serial in https://spring.io/projects/spring-cloud

[DevDengChao]

In document https://spring.io/projects/spring-cloud#adding-spring-cloud-to-an-existing-spring-boot-application 's Table 1. Release train Spring Boot compatibility section, there is no guiding for Spring Cloud 2021 serial is compatable with which version of Spring Boot like other Spring Cloud serials:

Ps: I found the compatiable Spring Boot version later in https://docs.spring.io/spring-cloud/docs/2021.0.0/reference/html/ .

Sorry that I didn't found the website's repository and opened it here.
If it is needed, I'll close this and re-open another if someone told me the correct repository.

[snicoll]

@DevDengChao Thanks for the report but this is the Spring Boot issue tracker, not the Spring Cloud issue tracker. I suggest reporting this against https://github.com/spring-cloud/spring-cloud-release and the Spring Cloud team can move the issue if that's not the appropriate tracker.