Spring Update @DynamicPropertySource examples regarding changes in Testcontainers

Backport of gh-29939

Comment From: sbrannen

Closed in 782ee34cb735c0d3f8e867f04efb31a4afe2b46d

Comment From: sbrannen

Reopening to address recommendation in https://github.com/spring-projects/spring-framework/issues/29939#issuecomment-1420876765

Comment From: sbrannen

Closed in c9841f37b6b04eb2007d1de0f58b86158d7524fe