Spring Simplify getInternalBeanFactoryForBean

This pull request simplifies getInternalBeanFactoryForBean in AbstractBeanFactoryBasedTargetSourceCreator and makes its intent more obvious.

The problem in https://github.com/spring-projects/spring-framework/issues/25801#issuecomment-698346498 does not apply to this patch since the mapping function in this patch does not modify/access the map itself.

This patch was generated automatically by the static analysis tool Logifix as part of a research project.

Comment From: sbrannen

This has been merged into main.

Thanks for your first contribution to the Spring Framework.